Airborne Network Is It Really Required

Published Date: 02 Nov 2017

The technology and infrastructure supporting air traffic control system hasn’t undergone much change in the last few decades. Most aviation vehicles (commercial and military) depend on ground-based stations for radar systems, takeoff, landings and course changes. Instructions are provided by the people sitting in ground stations, who monitor every flying object entering their aviation range. With the on-going technological advancements in the field of communication and networking, commercial aviation is an area of opportunity that could revamp air traffic control system.

The contents of this report gives a helicopter view of what parameters will need to be considered for the design of an ultimate network that would help to overcome present challenges of aviation industry and its interface with other systems on earth and space.

Airborne Network –Is it really required??

Present robust commercial aviation system pose many challenges for a safe and successful operation. It is expensive to maintain such humungous infrastructure and with every addition of new flights, the dependency on ground staff increases. Operational Errors and manual air controllers limit the number of flights in the sky. An optimum solution is required for addressing the existing challenges and the impending new ones. Airborne network can address these issues and also form the groundwork for aviation industry’s future.

Future of Airborne Network

The last Airborne Networks Conference was held in Las Vegas, NV on October 23-25, 2012.The future of Airborne Network future is to integrate with Global Information Grid (GIG) such that it becomes part of the Network Centric Warfare, combining all three major domains: Air, Space and Terrestrial. Satellite Communication system network currently provides connectivity for all space asset communication. Terrestrial connectivity is provided by Combat Information Transport System. With Airborne Network, there would be a seamless communication platform connecting all domains.

Architecture

The main feature of this architecture includes self-forming, self-organizing and self-healing network. It operates using Line-of-sight and beyond line-of-sight connectivity. The nodes are formed by the Airborne Networking Platforms (ANPs) which form a constant network for other ANPs to connect and disconnect from the network. This is a very complex network architecture and practical scenarios/challenges will require solutions to be designed as and when they arise.

Figure : Schematic View of Airborne Network

Network Management

This system will corroborate the operation of all network elements on-board. It forms an interface with the Airborne Network system to remotely manage the Airborne Network elements. This will be capable of monitoring the system health for faults and latency, by conducting passive testing of the network. Additionally, it will be capable of reporting the settings of all configurable parameters of the network elements and perform changes to these settings when authorized by the operators. This system reports the utilization of network elements and apply network policy changes for network resource allocation while managing traffic flow. It will be capable of detecting security threats and pre-empt unauthorized attempts of network penetration and deny service.

Gateways/Proxies

This system will enable interconnection of all existing legacy systems to IP based network. It will facilitate the transition of legacy on-board infrastructure, TDS (Tactical Data link systems), off-board transmission system and user applications to airborne network. The scope of legacy infrastructure is temporary, until the standard IP based transmission systems becomes effective.

Routing / Switching

This system will enable dynamic exchange of data to other platform/systems in the network irrespective of their topology. It will also be capable of performing static, dynamic or ad-hoc routing as need arises and provide seamless roaming without disruption. Preserving the network scalability is important for routing as the network is constantly changing in this network architecture. The routing/switching mechanisms will use metrics to calculate delay, hops, load, and error rate of the paths taken to route data.

Performance Enhancing Proxies

The user applications performance can be enhanced across the Airborne Network by including few techniques referred to as Performance Enhancing Proxies. This is required in cases of wireless network impairments such as limited bandwidth, long delays, and disruption in connectivity and data loss rates. Some of the techniques that can be employed include: a). Compression - to minimize the number of bits transmitted over the network b). Data bundling – combining (bundling) smaller data packets into a single large packet c). Caching - A local cache to save and provide data objects that are requested multiple times d). Store-and-forward - Queuing of messages to ensure message delivery to nodes which get disconnected for a period of time. Once reconnected, the stored messages are sent. e). Translation - certain protocols or data formats are translated with efficient versions developed for wireless environments. f). Embedded acknowledgments - Embed acknowledgements in header of larger information packets to reduce the number of packets sent across the network. g). Intelligent restarts - Used to detect when transmission has dropped and once re-established, resume the data transmission from the break point instead from the beginning.

Security Management Infrastructure

This is comprised of components, functions and products provided by external systems and/or within the systems. The products provide software based cryptographic algorithms, public keys, certificates and virus update files. This would help in providing multilevel security against user data, administrative data and transmitted data. This system will also detect intrusion and attacks and prevent them to keep the airborne network safe.

Quality of Service (QOS)

Based on the dynamic traffic conditions, QOS mechanisms will allow airborne network to make decisions on resource allocation. This will prioritize traffic based on the application or user class and would ensure that the higher priority flow is initiated in case of insufficient resources. QOS parameters are oriented toward performance, format, synchronization, cost and user. To ensure the sustainability of QOS, the link management system must manage QOS parameters and allocate resources in response.

TOPOLOGIES

Four topologies will have to be implemented for the future Airborne Networks. Following are the four topologies:

Space, Air, Ground Tether

What is Tethering?

It is basically a process of creating a direct connection between nodes of LOS and another ground or air node. A point-to-point connection is used to connect these nodes. There is connectivity to a ground entry point which is basically facilitated by SATCOM. These tether connections work almost like a switch, router or a hub in a normal network.

Flat Ad Hoc

It is basically creating network connections that are indefatigable. The nodes in this kind of topology find other nodes on a dynamic basis. The nodes to which they can connect to form a network decide this. The connection nodes are not decided before the network formation. The connections change based on the location and availability of the nodes.

Tiered Ad Hoc

This kind of network topology is just like the above but the hierarchies are decided on a dynamic basis. The data moves from higher level to lower level subnets. It is similar to networks with router switches, hubs etc. to connect users on a temporary basis.

Persistent Backbone

It is used to facilitate the connection between tactical subnets and provide a persistent bandwidth by flying at relatively stable orbits. These tactical subnets are basically taken as edge networks, which are relative to the backbone. Again, these kinds of networks are just like conventional networks consisting of routers, switches, hubs etc. to connect various nodes to the network.

PROTOCOLS

ANTP Protocol Suite

ANTP stands for Airborne Network and Transport Protocol. ANTP is designed to control the highly dynamic network environment. It is designed to exploit cross-layer optimization among OSI layers such as physical, MAC, Network and Transport layers.

Design and Modeling of ANTP Protocol

AeroTP – Supports TCP and end-to-end protocol

It is designed to work in aeronautical environment and to support TCP. It has various modes or services like reliable, nearly-reliable, quasi-reliable, best-effort connections and best-effort datagram’s. Reliable service is completely TCP and best-effort datagram service is completely UDP. Its uses depend upon what kind of service a particular application needs. There is header for AeroTP, which is basically used to convert TCP/UDP into AeroTP and vice versa.

AeroNP – IP-Compatible Network Protocol

This protocol is designed to provide services to the AeroTP protocol and its transport layer. AeroNP is IP-based protocol. It also facilitates congestion-control and error detection to transport layer protocols. It also helps to maintain priority queues for application data. Its header also contains geo-location data if the mission needs it.

AeroRP – Geo-location-Assisted Routing

It is a protocol designed to work in partially connected network when reactive and proactive protocols failed.

The forwarding table, like in routers, are based upon location information along with few updates. Next hop is decided with the help of metric called TTI (time to interpret). Ns-3 is used to simulate this.

Implementation

The implementation supports various features like maintainability, reliability, and data analysis accessibility. To make it maintainable, the complete implementation is done using Object Oriented Concepts. There is nothing to worry about data structures and other complexities.

For reliability, the implementation includes try catch feature to get errors during run time just like in Java programming module. For analysis, it has a logging system that is used to save data in some log files that is further analyzed. The basic implementation is given in figure below.

Figure : AeroNP protocol

The implementation is done in PYTHON, which includes 3 phases. At first, every protocol is implemented solely and all the functions are tested under functional testing and in the 2nd phase, components are combined together for integration testing.

In the final stage, deployment of the system is done in embedded processors on aircrafts and vehicles on the ground.

Applications

4-D Trajectory Flight Management

In regular 3-Dimensional space is used to calculate the trajectory of the flight in motion. But the fourth spatial co-ordinate "Time" is also important to calculate and plan the course of the flight. In the existing ground-based FMS (Flight Management System), the trajectory is formed by the system, but the prediction is very short timed in the order of 10-20 minutes. This helps the flight in planning the route without any conflicts with other flights flying in the given time.

With airborne communication systems in place, these trajectories are based on satellite communication rather than ground based radar systems. The Federal Aviation Administration(FAA) which is implementing a satellite based communication system based on the its new project NextGen is implementing an efficient model which will take Global Positioning System (GPS) to communicate with satellites and other flights. Apart from the information given from the ground based system the air-crafts will also be able to communicate among themselves to conflict with the ground based system and make a change in the trajectory, this process is defined as Required Navigation Performance (RNP). RNP deals with precise pre-determined paths, and optimally change the paths of navigation within the given air-space.

The system also helps in making the landing an easier job, with Optimized Profile Descent (OPD), the lowest thrust required to make a smooth landing is calculated. This takes into account wind, temperature and other flight paths. For this model to effectively operate other flight OPD’s must communicate with each other to make an idle thrust for landing.

http://www.geaviation.com/systems/products-and-services/air-traffic-optimization-services/performance-based-navigation/images/opd-zoom.jpg

Figure : Operational Profile Descent

With the 4-D Trajectory Flight Management in place, a predictable path of the flights course and improve the efficiency of the flights in times of congestion. According to FAA, using GPS is known to increase route efficiency and reduce delay by 38%. It also greatly reduces the amount of fuel consumed by 1.4 billion gallons and carbon emissions by 14 million metric tons.

A European based Air Traffic Management (ATM) which is similar to FAA also working on a similar model being developed as Single European Sky ATM Research (SESAR).

Air Force Operations

Figure : Global Information Grid

The US Air Force will use these networks to a wide extent and their traditional sensor to display system is moving towards a machine to machine system. Flights such as bombers, fighter jets and unmanned aircrafts are supported by a space system comprised of satellites.

Airborne networks are used to provide details to a missile about the moving target or provide a pre-strike demonstration on the target. It will also be employed in Joint Unmanned Combat Aerial Vehicle (JUCAV) where multiple aircrafts communicate with each other to give details about the target or its operations.

Sensors will still be present to be used along with airborne networks to give a collaborative data. This data is induced to a machine learning system, where the system learns and solves problems based on the previous occurred situation, thus commanding a better warfare.

Advancements in Electronic Flight Bags (EFB)

An Electronic Flight Bag is an electronic equipment which helps in displaying information on the various operations in a plane such as charts, manuals, positional and weather data. EFB is almost used by all air-carriers. EFB’s which are portable and are operated by satellite navigation provide details on the position of the aircraft in air-space as well are in ground level landing spaces. Satellite Broadband connections can be implemented on EFB when the flight is in air and in motion. They deploy moving maps to the system which give the location precisely in relation with the ground and the terrains.

Installed EFB’s are also deployed in aircrafts and it supplies reliable aeronautical information to the cock-pit. It has also been upgraded to give more safety enhancements to the aircraft. The altitude of the flight in relationship with other flights in the current air-space can be calculated and a safe distance can be maintained.

One of the key enhancements in EFB’s is while landing, in which it shows the precise location of the aircraft to the runway level. This greatly enhances the safety of the aircraft in very congested airports.

Weather Forecasting and Reporting

With Airborne Networks in place a lot of data can be communicated between systems in the airways. Weather Forecasting is important for operation of flights, depending on the weather the course of the flight or landing can be altered to increase safety.

FAA has implemented systems such as Weather Camera Program (WCP) and Integrated Terminal Weather System (ITWS) for air traffic management at airports. ITWS obtains weather information from various sources and provides it in a simple understandable interface. This helps the airplanes and controllers to navigate appropriately depending on situations. WCP provide video surveillance on remote airports where weather forecasting cannot be done effectively. An almost near-real-time video is broadcasted to the arriving flights.

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Figure : ITWS Application in Action

Weather and Radar Processor Sustain (WARP) is a system implemented to combine weather data with the existing controls of the on-board navigation systems.

Text Messaging, Web Services and VoIP

IP based machines and applications can be run on airborne network, making way for the inclusion of web services to the machines. All airborne machines will act as nodes and will be used for Communication, Navigation and Surveillance (CNS). These nodes can be used to communicate among air systems or air-surface systems. The data being transmitted will have a high bandwidth comparable to cable modems present on the surface systems. It works similar to the common internet which uses TCP/IP as the communication protocol.

The basic idea for incorporating such mechanism is to be a replacement for the traditional ground based communication infrastructures which are susceptible to disasters. Short Messaging Service (SMS) or Voice over Internet Protocol (VoIP) can be used to relay messages during catastrophic times, which could save human lives. These systems are built to be weatherproof and also work in circumstances where the airborne systems are in an airdrop.

In short term, Airborne Network would be able to eliminate Operational Errors in Communication - read back, hear back, transposed calls, signal failure, incorrect information, wrong aircraft are the most significant contributor for failures/crashes and enables smoother air traffic flow. It would also help in optimizing routes for reduced travel and traveler’s time, reduce fuel consumption. Long term contribution would be to incorporate more flights in sky with no additional infrastructure, also increase the number of flights in and out of smaller air fields, even with no radars.

Challenges and Plausible Solutions

Dynamic Network

Airborne Networks maintenance is not as simple as an Internet connection. The infrastructure of the system varies dynamically from time to time. When a flight system goes from one network to the other network, it has to change the node properties to quickly adapt to the new setting available.

It requires a high level of automation as there will not be a technician sitting to control the system on the plane. So the network must form by itself allowing for operations depending on the situation. A very high fault tolerant machine must be installed to make this possible.

Optimization of Resources

Aircrafts are known to have only a limited supply of resources on board. So the physical space for the equipment on the aircraft is limited. Airborne Network does not depend on one simple technology to do its operations. Commercial off-the-shelf (COTS) equipment can be a solution for cheap and readily available resource. But COTS has lots of engineering challenges, like it cannot adapt itself to various application and protocols. For example, according to the Radio Technical Commission for Aeronautics (RTCA), to set up the advanced equipment on a flight it would cost from $150,000 to $650,000 for Required Navigation Performance (RNP) package, which is an important resource to implement the precise systems. So a new breed of networking concepts are required to address the limitations based on the resources.

Secure Network

Huge volumes of data will be transmitted in an airborne network and the data which is transmitted needs to be secured. For Passenger carrier flights the security of data being transmitted may not be very important, as they only focus on less details such as flight details, navigation routes and weather data. But in case of military flights, there is a lot of confidential data being transmitted over the network so it is necessary to make it much more secure. The network should also have lower chances for congestion and prevent security threats like interception and jamming.

Huge volumes of sensitive data are being transmitted through the airborne network in military infrastructures. Geo-coordinates of military vehicles are classified and require high levels of security. Data containing details of military images, warfare strategy information, and weapon characteristic data needs to be encrypted before they are transmitted. And the accreditation
process to make this a standard takes more time to complete, than the time to build the product itself. So a faster means of accreditation is required to make it a standard.

Band-width Availability

Inherently the data speed rate of the Airborne Network is lower than the terrestrial networks. More number of optics is required to be incorporated into the system to increase the bandwidth and the latency. Some of these technologies are still under research, the Navy wing of US is working on an integrated photonics which will help in managing the sensor suites present in the aircraft for communication. This concept tries to implement radio signals to pass via fiber optics for better data speeds.

Airborne network does not have a dedicated bandwidth to support its operation. So there is a challenge to create more efficient data compression techniques. A temporary resolution is being provided by Northrop Grumman, a global aerospace technology company, where Dialup rate IP over existing radios (DRIER) is using the basic computer IP to make communications.

Acronyms

ANP Airborne Networking Platforms

ANTP Airborne Network and Transport Protocol

ATM Air Traffic Management

CNS Communication, Navigation and Surveillance

COTS Commercial off-the-shelf

EFB Electronic Flight Bags

FAA Federal Aviation Administration

FMS Flight Management System

GIG Global Information Grid

GPS Global Positioning System

ITWS Integrated Terminal Weather System

JUCAV Joint Unmanned Combat Aerial Vehicle

OPD Optimized Profile Descent

QOS Quality of Service

RNP Required Navigation Performance

RTCA Radio Technical Commission for Aeronautics

SESAR Single European Sky ATM Research

SMS Short Messaging Service

TDS Tactical Data Link Systems

TTI Time to Interpret

WARP Weather and Radar Processor Sustain

WCP Weather Camera Program

VoIP Voice over Internet Protocol