Tuesday, January 3, 2017

Connected Airplane 2017 - Are we there yet?

Connected Airplane 2017 - Are we there yet?

It is the beginning of 2017, the prospects could not be more interesting.  Look below for a brief status and key technologies stepping through each network.  Included are links to other articles digging deeper into each the topics.

Network Security is front and center with every service provider and every operator and airspace manager.  Standards based security, using certificates and encrypted IPSec tunnels, are the threads that will form the emerging fabric to secure aviation networking.

Broadband comms (satcom, ATG) are rapidly evolving to meet the needs of passengers.  The cost point for equipment may not be improving dramatically as efficiency is offset by complexity.  The cost point for service is reducing aggressively, due largely to spot beam frequency reuse.

Emerging broadband technologies include:
While emerging technologies are compelling, the real challenge is figuring out who will pay for passengers to use the service, and how much money is there in the business.  I am confident we will find a way to succeed, but it is always a chase with fixed satellite, cellular, and wired solutions far ahead.

The combination of enhanced comms (direct pilot/conroller data link and voice, ADS-B, ADS-C) leading to enhanced surveillance and coupled with RNP/GNSS based navigation are the foundation for air traffic management.  While the technologies are relatively stable or incremental, the real challenges are, as always, procedural and cost.

Network Security

Whether comm, nav or surveillance, radio transmission are the foundation for air traffic management and for connecting the occupants and the systems to the Internet.  Radio transmission are especially vulnerable, whether air-ground or in-cabin, to weaknesses in security.

Most emphasis today is placed on security between the airplane and the ground station, relying on a trusted relationship to complete the connection to the appropriate resource.

A significant disconnect exists between how each radio system is secured itself, and how each application uses each radio system.

The migration to IP-based networking enables incorporating mainstream network security that can extend across untrusted domains spanning both the air-ground radio and the intermediate ground-ground Internetwork.

KEY TECHNOLOGIES: Existing methodologies are layered upon one-another to create a trusted end-end secure connection.  Certificate-based authentication and IPSec Virtual Private Network (VPN) coupled with encryption form the basis of Project Paper 848, ATN-IPS, and IRIS-Precursor network architectures.  The differences lie in how far end-end the VPN terminates.

Cybersecurity - PP848
Security, Segmentation, QoS - PP848
Secure Networking

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Passenger Communications

Early Ku Satcom - CbB and ARINC/ViaSat
The 2000's marked the emergence of Ku band services promoted by Connexion by Boeing and ARINC/ViaSat. The technology was stunted by commercial challenges overcome in the next ten years by better modem and network management.

KEY TECHNOLOGIES: CDMA modems lost favor due to their need for leasing whole transponders.  TDMA modems allowed emerging service providers to invest in only small slices of transponders.

Early/Contemporary ATG - Aircell/Gogo
Aircell, starting in the early 1990's with a reuse of cellular frequencies.  They later brought Gogo to life in the late 2000's with 3 MHz (but now 4 MHz) of dedicated spectrum.  ATG-4 brings data rates to one airplane up to about 10 Mbps.  However, the number of stations and thus available channels has been overcome by demand and can become saturated.

KEY TECHNOLOGIES: Enhanced modems brought higher spectral efficiency.  A second terminal (antenna and modem) allowed bonding service to two ground stations, effectively doubling capacity.

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Contemporary Wide-beam GSO Ku/Ka Satcom
While ATG-4 is still a useful service, especially for general aviation, Gogo has turned to satcom for boosting service levels and to gain a global footprint.

ViaSat, Gogo, GEE, Panasonic, Inmarsat, Thales are the current Ku/Ka satcom service providers.

Regional service providers are beginning to creep in, benefiting from national concerns, and off-the-shelf technology.

Echostar/Hughes may emerge as a stand-alone provider, or remain as a supplier to the other service providers.

SES and Intelsat are positioned as a supplier to the service providers.

ViaSat and Inmarsat are launching their own satellites, and leasing to augment.

Panasonic and Thales appear to be funding hosted payloads, bringing them half-way between Gogo&GEE Vs Inmarsat&ViaSat.

LiveTV and ViaSat promoted their Exede service with the launch of ViaSat-1.  ViaSat has forged partnerships to gain Ka-band coverage in other areas.   ViaSat awaits the imminent launch of ViaSat-2 to significantly increase the available capacity over a much larger coverage area.

KEY TECHNOLOGIES: DVB-S2X modem brings off-the-shelf capability to operate with heavily disadvantaged terminals (e.g. aero).

KEY TECHNOLOGIES: GEE/QEST offers interchangeable Ku-band or Ka-band tri-axis multi-gimbal antennas.  This antenna can be installed into the same provisions as a TECOM antenna, but offers a third axis to reduce the effects of skew angle.  While the inherent aperture remains about 1/3 the size of 2Ku and stands several inches taller, it is much lighter and it offers good performance to as low as five degrees elevation (for high latitude routes).

Skew Angle

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Emerging Spot-beam GSO Ku/Ka Satcom
Spot-beams allow for frequency re-use.  Frequency re-use boosts the available capacity of a satellite in comparison to wide-beam transponders.  Every service provider is pursuing spot-beam solutions, also known as High Throughput Satellite (HTS).

KEY TECHNOLOGIES: Ka-band spot beams are smaller than Ku-band spot beams using the same sized aperture.  Smaller spots means higher gain means more spots means more frequency reuse.  Unfurlable apertures are enabling larger apertures to reduce spot beam size for Ka (ViaSat-2) and for Ku (Panasonic XTS).

KEY TECHNOLOGIES: Spot-beams can dedicate larger carriers to support much higher data rates on the forward channel, while not significantly boosting spectral efficiency.  Carriers originally limited to less than 36 MHz may now span as much as 500 MHz.  

KEY TECHNOLOGIES: Satellite transponders have limits to the power available to them.  While spot beams create a network of cells, it is not likely that enough power exists to light them all up simultaneously with maximum reuse.  Means to shift transponder carrier power, such as ViaSat beam-hopping, allows capacity to follow demand wherever it emerges.  Regardless, one satellite can only light up one spot with its spectral assignment, and that may not be adequate for the demand, required overlapping coverage.

KEY TECHNOLOGIES: Spot-beams inherent G/T advantage (10 dB or more) over wide-beam makes the under-performing return channel from struggling to offer 1 Mbps to as much as 10 Mbps.

KEY TECHNOLOGIES: The feeder link to a satellite connects the ground station while the service link to a satellite connects the client.  The network to service the service link is mirrored in the feeder links necessarily to complete a connection.  The spectrum to support each link must be exclusive to each other.  This creates competition and generally a need to segregate the two beam sets in some way.  Some Ku satcom are leveraging Ka feeder links, while all Ka satcom are currently only using Ka feeder links.  The bottom line, the feeder network of ground stations represents a large and complex investment when deploying spot beams.  This adds cost to the network deployment, and entails proprietary modem technology to manage.

It Takes a Village
Show Me the Gbps: When 1+1 > 2
Average Data Rate and Usage
My Take on Take Rate
Cisco Mobile Forecast
Average Broadband User
50-80 users contention
Are Spot Beams better than Wide Beams?

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Generic Satellite Technology
Satellites are custom designed in a process that may take two-four years from contract to in-orbit operation.  The cost for developing a custom satellite creates a barrier in addition to the long time to respond to market demand.

KEY TECHNOLOGIES: Reflectarrays are enabling software-defined coverage patterns.  Means to shift capacity dynamically coupled with flexible coverage patterns enables a generic satellite payload.  A generic satellite payload offers lower capital expense and shorter time to market.
Launch Vehicles
The cost of in-orbit insertion is based upon the cost of the equipment used to launch.

KEY TECHNOLOGIES: Reusable first stage rockets will lower the capital cost to launch satellites.

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Emerging NGSO Ku/Ka Satcom
Non-Geostationary Orbit (NGSO) satcom constellations are rampant.  O3b (MEO/Ka) and OneWeb (LEO/Ku&Ka) appear to be the most in the lead.  The aero terminal for NGSO will likely be as large as for GSO, in spite of their closer proximity to the servicing satellite transponder.  In fact, it may be more complex to allow for dual beam receive, frequent handoffs, and steering through zenith.  The overlap of GSO to NGSO is also a factor in building enough coverage and capacity.  NGSO capacity over a given spot on the earth is not easily increased.

KEY TECHNOLOGIES: Phased array antennas may be most suitable for NGSO applications.

NGSO spectral assignment are still being worked out. GSO and NGSO profess to work together, each suppressing emissions if the primary user is in view.   However, NGSO sharing amongst themselves is still a work-in-progress.  The FCC professes band-splitting while the industry favors either a monopoly or cooperative solutions.  These issues will get more interesting when the overlap involves the feeder links.

KEY TECHNOLOGIES: Agile frequency management that responds to changing spectral capacity as a function of intruding satellite constellations.

OneWeb - Key Characteristics

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Emerging Flat-Panel Antennas
Aero antenna technology is evolving to favor flat-panel antennas.  A large flat-panel antenna (1500 sq in) can operate down to five degree satellite elevation.  Passenger demand is insatiable.  Larger apertures are the only hedge aero terminals can bank on for both achieving high data rates and for cost-efficiency.

Aero Antennas: Bigger is Better!

KEY TECHNOLOGIES: MMIC and ASIC based phased arrays, meta materials, and VICTS are enabling flat-panel apertures.  The real-world performance of each technology is still being assessed, with concerns around beam walking (due to wide carriers on phased-arrays), high noise floor (inherent in MMIC/ASIC technologies, but improving), temperature/vibration/shock stability, and beam steering reliability (difficult to detect failed elements, slaved open-loop steering).

KEY TECHNOLOGIES: Overlapping apertures (transmit and receive) would be an exciting feature to allow for larger apertures in the same space.

KEY TECHNOLOGIES: Dual-beam receive would offer a second receive beam independent from the first (each with full effective aperture).  The second beam can be used for broadcast reception (live TV), while the first receive beam and the transmit beam provide for Internet access. Dual-beam receive may be available only in some phased-array technologies.  Dual-beam receive is also useful for make-before-break satellite handoffs.

KEY TECHNOLOGIES: The first of the flat-panel antennas, Gogo/ThinKom 2Ku antenna offers dual 30" apertures.  While suffering scan loss that degrades performance when the satellite is below 20 deg elevation, the large aperture delivers higher performance than other antennas when steered above about 20 degrees elevation.  Furthermore, the skew angle effects are tempered in comparison to other antennas, especially while the satellite is reasonably above the horizon.  

Second-Generation Satcom - PP792
Phased Arrays

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Emerging Unlicensed Spectrum ATG
Unlicensed (e.g. 2.4 MHz ISM band) is gaining favor for line of sight (LOS) services.  SmartSky and Gogo have publicly stated their intention.   Performance remains a marketing exercise.  Concerns remain over the impact of the noise floor.

KEY TECHNOLOGIES: Beam forming array (15.247 Smart Antenna System) at the ground station enables sufficient gain and isolation for long-distance communication.

15.247 Smart Antenna System
Harris Grant (SmartSky)

Emerging Hybrid ATG/Satcom
Inmarsat and T-Mobile are launching the European Aviation Network (EAN).   Through careful coordination, satellite spectrum is re-used to power an underlying cellular network and the overlying satellite network.  The installation of two ATG radio/antennas and one satcom terminal makes it the most complex system.

KEY TECHNOLOGIES: Re-use of S-band spectrum and almost off-the-shelf LTE modem technology.

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Decision by Apple to remove the headphone jack in favor of bluetooth coupled with the maintenance and cost of an in-seat jack and network makes bluetooth in the seat highly likely.  Once bluetooth access points are present in every seat, new features may emerge.


Bluetooth Low Energy

IEEE 802.11 variants have been installed to serve Wi-Fi to passenger devices and other aircraft terminals (e.g. portable).  The 5 GHz band expands the number of overlapping channels from 3 (2.4 GHz band) to 23 channels. Access point placement should be distributed at least into two locations. A single access point may support one 2.4 channel and two or more 5 GHz channels, allowing for scalable services.

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Pilot/Controller Communications

Historically we have had line-of-sight (LOS) VHF voice and ACARS packet data.
  • VHF Plain old ACARS (POA) using MSK:2.4 kbps
  • VHF Data Link Mode 2 (VDLM2) using D8PSK:31.5 kbps
We are still migrating everyone to VDLM2.  The acceptance of ACARS data link for domestic use (FAA) has brought a bit of life to POA.  The capital expense to transition to VDLM2 is offset by the willingness for the data link cost of air traffic control to be subsidized by the air navigation service provider in comparison to POA which costs may be fully borne by the operator.

KEY TECHNOLOGIES: 25 kHz VDLM2 and 8.33 kHz voice are the VHF foundation for the foreseeable future.  VDLM2 can support both ATN-B1 and Plain old ACARS.

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HF (shortwave) voice and ACARS data (low speed) offer beyond line-of-sight (BLOS) communications encumbered by diurnal frequency preferences and varying voice quality.  It is my personal goal for more than 20 years now to fully replace HF with satcom.  However, the glacial pace and continuing investments in HF technology are slowing the transition.  Our greatest hope is to build an airplane with one HF and one satcom for voice as the next step.

KEY TECHNOLOGIES: An airplane with two satcom systems (likely diverse) and no HF remains a goal perhaps ten years hence.  We have the technology to do it today.  We lack the operational framework; to that end I am hopeful Transport Canada will continue to showcase the benefits of Direct Pilot-Controller Voice.

Satellite Voice

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Back in 1990 we started with low speed Inmarsat L-Band satcom.  A packet data network connected ACARS at less than 300 bits per second (a fraction of the 2400 bps we had available over VHF with MSK modulation).  By 1993 we had high gain connections capable of about 5200 bps (packet) and the addition of a 9.6 kbps voice codec and a 2.4 kbps circuit switched data (V.22bis) connection.  Iridium finally brought a compact LEO solution eventually bringing a useful packet service (SBD) and voice over a global footprint.  Iridium and Inmarsat operate on adjacent frequencies and this has created significant challenges co-locating these terminals on the same airplane.

Inmarsat continued with Swift64 (S64) and now SwiftBroadBand (SBB) capable of hundreds of kbps over the same small slice of protected L-Band spectrum.

KEY TECHNOLOGIES: smaller high gain antennas offer access to higher and higher data rates due to modem enhancements (bonding, mod-cod).  SB200 brings high speed packet data and voice to a low gain antenna.

Inmarsat and Iridium offer satellite spectrum that is approved for air traffic control communications.  While legacy ACARS networks operated at low speed. SBB safety brings approved high-speed IP networking.  Iridium Certus initially plans to continue using SBD for ACARS, but has a path to a high-speed IP channel as well.

KEY TECHNOLOGIES: Higher speed modems coupled with safety-approved spectrum (Route-  AMS(R)S) give ACARS data link a long-life ahead.

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Data Link
Eurocontrol has remained steadfast in favoring ATN over ACARS.  This has led to a bit of a break from the rest of the world and the need for a second dedicated network capability: SESAR ATN-B1.  Eurocontrol has struggled with the VDLM2 network capacity and has just started with Inmarsat to offer an alternative L-Band (IRIS precursor) satcom pathway.

KEY TECHNOLOGIES: ATN-B1 relies on x.25 inter-network only available in Europe.

The rest of the world (and notably FAA domestic) is following an ACARS pathway.  FANS, now 20 years old, is the data link technology for the foreseeable future.

KEY TECHNOLOGIES: With ACARS, FANS relies on ARINC 622 ACARS convergence function and ATS facilities notification coupled with the ATN message set (common reference with ATN-B1).

KEY TECHNOLOGIES: ATN/IPS initially will focus as a secure bridge (IPSec tunnel) between the ACARS router and the data link service provider (DSP).  In this manner, existing FANS/ACARS based ATN messages can be transferred to IP networks without expensive upgrades to the intermediate and end-systems.

Safety Networking

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AeroMACS is moving quickly for launch to take benefit of 59 MHz of safety-approved spectrum.  While the terminal technology is evident, the buildout at each airport and the commercial arrangements between the FAA, the airports, the service provider, and the airlines seems still a work-in-progress.

KEY TECHNOLOGIES: Adherence to WiMAX (802.16) and dedicated spectrum solve the greatest technical challenges with a new service provider.

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FANS surveillance relies on a data link application called ADS-C.  ADS-C is an ACARS message.  Current low-speed ACARS satcom transmissions have struggled to meet the RSP-180 requirement necessary for 30 nm longitudinal separation.

KEY TECHNOLOGIES: With SBB Safety IP-based ACARS messaging, higher performing surveillance and data link are possible - perhaps less than 30 seconds.

Aircraft surveillance technology is undergoing a sea-change.  The advent of Multi-lateration (MLAT) and ADS-B has completely upended Secondary Surveillance Radar (SSR).  Primary Surveillance Radar (PSR) remains for intruder detection.  Crowd-sourced aircraft tracking (e.g. flightradar24.com) opens a whole new dimension to airspace applications.  Space-based ADS-B receivers (e.g. Aireon) are creating an overall surveillance capability using 1090 ADS-B Out signals already widely mandated.  "Floatradar" (flightradar24.com using the Boeing/Liquid Robotics platform) autonomous maritime platform enables another means for oceanic coverage.

KEY TECHNOLOGIES: ADS-B Out (1090 MHz Extended Squitter) is the building block for aircraft tracking and for airspace management.

Aircraft Tracking: ADS-B

satcom.guru ADS-B accident reports:

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ADS-B In is the receipt of ADS-B Out information from adjacent airplanes.  TCAS offers a similar capability, relying on signal strength to determine bearing.  The mix of ADS-B In and TCAS offers local validation of the ADS-B Out information.  Crowd-sourcing TCAS and ADS-B In data may open up new surveillance opportunities.  In the mean-time, controllers are increasingly willing to  delegate separation using ADS-B In to allow close-spaced maneuvering and more efficient flight profiles.

KEY TECHNOLOGIES: ADS-B In situation awareness coupled with features and procedures tied to the Air Navigation Service Provider allowing close-spaced maneuvering.

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ICAO professes enhanced tracking capability in response to AF447 and MH370.

By 2018, aircraft should have normal position reported every 15 minutes.  This is already routinely accomplished using ADS-C.  ADS-B reporting would offer updates as little as 10 seconds, and ADS-C using SBB-safety may be able support 30 seconds or less.

KEY TECHNOLOGIES: ADS-C offers global coverage (Inmarsat does not cover polar regions). ADS-B coverage is regional today, but in the next two years may have compelling global coverage from space-based providers.

By 2021, aircraft should have autonomous distress tracking capability (ADT).  This entails one-minute reporting by a system that can operate autonomously (without power) and in defiance to tampering.  ADS-B, ADS-C and ELT are all candidate technologies, but the installation would need revisions to ensure autonomous and tamper-free

KEY TECHNOLOGIES: A radio the relies on a self-contained antenna and battery power is a necessary aspect that currently seems best met by ELT, 1090ES, or Iridium-based terminal.  The radio should operate with the airplane undergoing unusual attitudes.  Investment in an Iridium-based terminal allows concurrent applications while not in distress mode.  ADS-B (1090ES) ability to operate under battery power remains uncertain.

Aircraft Tracking: ADS-B

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Stay tuned!

Peter Lemme
peter @ satcom.guru

Follow me on twitter: @Satcom_Guru

Copyright 2017 satcom.guru     All Rights Reserved

Peter Lemme has been a leader in avionics engineering for 35 years. He offers independent consulting services largely focused on avionics and L, Ku, and Ka band satellite communications to aircraft. Peter chairs the SAE-ITC AEEC Ku/Ka-band satcom subcommittee developing PP848, ARINC 791, and PP792 standards and characteristics. 

Peter was Boeing avionics supervisor for 767 and 747-400 data link recording, data link reporting, and satellite communications. He was an FAA designated engineering representative (DER) for ACARS, satellite communications, DFDAU, DFDR, ACMS and printers. Peter was lead engineer for Thrust Management System (757, 767, 747-400), also supervisor for satellite communications for 777, and was manager of terminal-area projects (GLS, MLS, enhanced vision).

An instrument-rated private pilot, single engine land and sea, Peter has enjoyed perspectives from both operating and designing airplanes.  Hundreds of hours of flight test analysis and thousands of hours in simulators have given him an appreciation for the many aspects that drive aviation; whether tandem complexity, policy, human, or technical; and the difficulties and challenges to achieving success.


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