
The United States has the world's most advanced and safest air navigation system. The problem with a mature successful system is for the vendors; while there's a minor upgrade every few years, the Industry really doesn't get to sell any more major new systems.
Unless they get some magic beans that will change everything. What would be an attractive list of

What are the vendors selling? Are they going to develop a startling new technology for their share of the public treasure? No, they're going to
GPS is the basis of Industry's NextGen bundle, because it provides a capability that Industry doesn't have to pay for or maintain. It's free; it's ubiquitious.
Unintended Consequences of Free and Ubiquitious
The problem with free and ubiquitious is that people start using it for creative secondary reasons, and those applications can bring unintended consequences to other participants.
Unfortunately, LightSquared's use of their spectrum caused problems for everybody's GPS.

Without getting too technical, GPS uses a satellite way up high to send a teeny weeny faint radio signal to your WalMart GPS which was produced on razor-thin margins. In other words, GPS requires a cheap-as-possible device to receive and process a very faint signal. For a long time it worked, because nobody was using the adjacent spectrum.
LightSquared wanted to use the adjacent spectrum and place fairly relatively low-power transmitters all around cities (with airports) to provide MetroWiFi. Their low power tranmitters put out a much stronger signal than the far-away satellites.

There's nothing wrong with LightSquared's technical approach. The problem is that billions of existing GPS receivers aren't shielded for interference, and aren't built to identify the legitimate satellite signal. LightSquared unintentionally exposed an essential, flawed assumption in relying on GPS.
LightSquared lost because the Homeland Security Military Industrial Complex (HSMIC) commissioned studies and wrote papers that said, Establishing low-power transmitters in LightSquared's spectrum will disable all GPS air navigation for that region. Wow. wow Wow wow Wow. wow.
We have no love for LightSquared or Falcone, who was attempting to become rich by exploiting an undervalued national asset, which is a bit like stealing from your children. It is intriguing that the HSMIC would publicly confirm that a series of low-power transmitters could disable GPS air navigation just when we're about to throw away the
I mean, Holy Asymmetric Warfare, Batman! Haven't we recently seen American aviation grounded by asymmetric techniques? Are we really about to decommission the existing robust, decentralized system and replace it with something that can be disabled with a few low-powered transmitters?
The Asymmetric Scenario
Here's the script: a non-state, religious-based network that's upset because we're occupying their 'stan places electronic transmitters in ten US metroplexes. The transmitters are innocuous; they look like laptop power supplies. They're programmed to turn on and off in a consistent, intermittent pattern during the day; each city's network will go active two days a month. Monday it's Newark; Tuesday it's Dallas; Wednesday is LosAngeles; Thursday is Chicago; Friday is Atlanta. Week two is Philadelphia, Boston, San Francisco, Houston, Seattle. Get the flick? They plug these devices in on the first of the month and walk away; they're in storage units, rental houses, etc. They've just shut down the domestic GPS aviation system, because the uncertainty is unacceptable.To be fair, radio-based air navigation has always been subject to intentional, adversarial interference (MIJI). It's nothing new. The difference is that existing systems can be overcome by high-powered transmitters and those are relatively easy to find and deal with. The faint GPS signals can be thwarted by a few low-power transmitters that are very hard to find when deployed as a noisy network.
- The early concern about switching to NextGen is: China can shoot down satellites, and NextGen requires satellites.
- The asymmetric concern about NextGen is: a very low cost, hard to track, easily deployable grid of low-powered transmitters will render GPS unusable to aviation, and NextGen requires GPS.
I find the second issue (asymmetric vulnerability) more concerning than the first (China). But now it seems that the greatest risk of all is a guy named Vinny and the housewives of New Jersey, and the many people like them.
NextGen ATC vs Vinny & the Housewives of N.J.
Here's a story. The facts are fudged but there's truth in it; there are links to the official reports below. There's a guy named Vinny who lives in Fort Lee, New Jersey with his wife. Vinny's girlfiend lives in Passaic, which is far enough away that they're not likely to see each other in church, but close enough that he can get over there occasionally.
Vinny thinks the wife suspects something. She watches Housewives of New Jersey, which is kind of an aspirational drama for her. Vinny knows The Wife could slip a GPS tracker into his car and he'd never know it, so he seeks advice from his cousin Joey.
Joey works for a delivery company where they put GPS trackers in every vehicle to optimize efficiency - which means, keeping the guys from napping. His cousin went to Google and typed in, GPS blocker jammer and found a solution. Now on rough days Joey turns on the jammer gizmo, drives to a park and takes a nap. Fuggedaboudit.
Vinny does the same thing. He buys a personal GPS jammer and turns it on before he sneaks over to Passaic for an assignation. Unfortunately, when he drives by Newark Liberty Airport on the Turnpike, his GPS jammer blocks the GPS signal. Two pilots report the outage and it's a major snafu. The technicians come out but now everything's working fine because Vinny has moved on. At the airport people try to figure out what happened over coffee and bagels; it's hard to troubleshoot a phantom event. Fuggedaboudit.

About ninety minutes later, the pilots are reporting GPS problems again. Guess what? Vinny is going home to Fort Lee. The technicians scurry all around and chaos reigns again, but a while later everything seems fine.
Both Fox News and The Economist carried this story. The geeks are all over this; WIRED magazine's article was titled, The $30 GPS Jammer that could paralyze US Cities, and they suggest there's a lot more involved than aviation, because a lot of embedded systems use the GPS time-stamp as an essential component.
The Newark Airport has never been able to commission their public-private-partnership (PPP) Honeywell GPS ground-based augmentation system (GBAS) in spite of their great desire to do so, because between deliverymen and philandering spouses like Vinny, there's a lot of people on New Jersey highways with GPS jammers.

Back to Vinny. We don't know if Mrs. Vinny ever got a GPS tracker, all we know is that Vinny is a weasel scoundrel who was afraid of being discovered. He was afraid she could be a wannabe Housewife of New Jersey and buy a GPS tracker, so Vinny invested in some electronic countermeasures (ECM). (Probably, next season, the Housewives will deploy drones.)
Vinny's compromise of the Newark airport was driven by his desire to not get caught in adultery. That is a rational, non-trivial, universal motivation.
Any engineering system faces forces that would work against it. Bridges, for instance, must deal with wind and tides. If NextGen has to contend with nervous adulterers for operational reliability, it is doomed from the start. And I think that's an argument that most Congressmen could relate to.

China? Fuggedaboudit. Think about Vinny and the recent LightSquared documentation, and the wisdom of replacing the legacy system with a GPS system.
