by Kevin
A Revolutionary Product
In 1995, a small team at General Dynamics (then Motorola) demonstrated a new communication system for the military. It was called COBRA, and it brought a revolution to the process of "Blue-Force Tracking."
The Blue Forces are the good guys. It's crucial to know where they are on a battlefield, and the more precisely, the better. The COBRA system was the first one that built GPS receivers directly into the transmitters. Further, the COBRA receiver produced reports that could be sent to a command center on the other side of the world.
The military went wild for our system. For the next few years our prototypes were in constant demand, being set up and demonstrated in operations all over the world.
Ongoing Research
While our team worked to ship units around and keep them supported, I continued research on the prototype design. One of my contributions was an unconventional parallel PLL function that increased the detection bandwidth of the receiver by a factor of 50. Another was an implementation of the receiver algorithm among parallel DSP processors.
I also did my share of field support. I would ship transmitters, receivers and all the support equipment and drive out with it to some remote site in the desert, run up the antenna, and start tracking assets. A fun assignment was when I got to join some Air Force guys on top of a mountain in eastern Washington, then ride in a Blackhawk helicopter back to Spokane.*
The Day Everything Changed
Everything changed when the World Trade Center was attacked. On September 10 of 2001, we had about 50 prototype transmitters and a few wire-wrapped prototype receivers in circulation. On September 12 we got an emergency order from our customer:
- Bring our current prototype transmitter to production status -- in TWO MONTHS.
- Be ready to deliver 500 of them a few months afterwards.
- Get started on a production-status receiver, too.
My role in this? Math, math, math! In addition to continuing to optimize the receiver algorithms, I worked hand-in-glove with our FPGA engineer to support his designs. I wrote simulation after simulation and generated test vectors for lab testing.
Indiana Jones and the Deployment of BFT
My other full-time job was deploying and operating the new receivers and transmitters, first around the country, then around the world. I never thought my minor in communication systems would lead to adventures such as:
- Flying in a C-130 doing simulated missile evasions over the Nevada desert -- followed by a very real emergency landing.
- Climbing a 100-foot water tower in the Florida panhandle while surrounded by wasps.
- Driving a terrifying cliff trail to the top of a mountain near Yuma, and camping for the night in a blockhouse full of spiders.
- Relying on my 13-year-old smattering of Japanese to translate for our team in Okinawa.
A big part of the job was figuring out how to get BFT reports out of the remote site and into the dissemination networks. T1 connections, encrypted-Ethernet-in-the-sky, any available data link was fair game.
We had a lot of success using the modem attachments on Iridium phones, but somehow I had to bring up a TCP/IP link across them. (I used PPP.) I was able to link two Linux laptops by connecting from one laptop, to an Iridium phone, up to the satellite, down to the other phone, and to the second laptop while sitting at my mother's backyard table. Within days we had my Iridium lash-up flying around on a C-130. (See above.)
The best complement I ever received was when our customer specifically directed the program manager to send me, because "he had to know that it was going to work."
We Made a Difference
In the end, we fielded tens of receivers and several thousand transmitters. They were a tremendous asset in the War on Terror.
On a personal note, my first deployments to Hawaii inspired me eventually to move there, and to pursue a second career as a scuba instructor. But that's another story.
*Unrelated note: I wrote my master's thesis on helicopter flight controls, but never actually got to ride in one until then. My advisor and I had argued about the existence of something called a "nonmiminum-phase transmission zero" that we both agreed would be very dangerous. He said they would never field a helicopter with those dynamics. I saw one emerge clearly from the flight equations.
This was my chance to talk with an actual helicopter pilot, and he confirmed that yes, it existed, it was dangerous, and the solution was the same one I derived from the math (lower the stabilator). Sweet, sweet vindication!
