Slashdot Mirror
DARPA Begins Work On 100Gbps Wireless Tech With 120-mile Range
MrSeb writes "DARPA has begun development of a wireless communications link that is capable of 100 gigabits per second over a range of 200 kilometers (124mi). Officially dubbed '100 Gb/s RF Backbone' (or 100G for short), the program will provide the U.S. military with networks that are around 50 times faster than its current wireless links. In essence, DARPA wants to give deployed soldiers the same kind of connectivity as a high-bandwidth, low-latency fiber-optic network. In the case of Afghanistan, for example, the U.S. might have a high-speed fiber link to Turkey — but the remaining 1,000 miles to Afghanistan most likely consists of low-bandwidth, high-latency links. It's difficult (and potentially insecure) to control UAVs or send/receive intelligence over these networks, and so the U.S. military instead builds its own wireless network using Common Data Link. CDL maxes out at around 250Mbps, so 100Gbps would be quite a speed boost. DARPA clearly states that the 100G program is for US military use — but it's hard to ignore the repercussions it might have on commercial networks, too. 100Gbps wireless backhaul links between cell towers, rather than costly and cumbersome fiber links, would make it much easier and cheaper to roll out additional mobile coverage. Likewise, 100Gbps wireless links might be the ideal way to provide backhaul links to rural communities that are still stuck with dial-up internet access. Who knows, we might even one day have 100Gbps wireless links to our ISP."
It should be doable, providing two conditions are allowed:
1. The equipment may be ridiculously expensive (No problem: Around half the US government's budget goes to defence).
2. It'll need to be such high (analog) bandwidth, it'll not comply with any spectrum or power regulations, anywhere (No problem: If you're invading a country, you don't need to be overly concerned with obeying local laws, and even occupiers get some leeway).
I don't know why I'm responding since you're AC and won't see it, but if someone else is wondering the same thing, you can hear an FM radio broadcast for a couple hundred miles in some conditions. That radio station has a 50,000 watt transmitter, but the power drops off inversely. By the time it reaches your property it's only milliwatts.
Free Martian Whores!
How? Is it airborne or something? You are not going to get any straight line reception at that range due to curvature of the earth, even in the plains.
And if you manage high-bandwidth 125-mi range, the next step is obvious - a constellation of LEO (200-500mi altitude) satellites serving as a nearly-untouchable* backbone for the theater-WAN.
*ok not for peer-level opponents, but I'm pretty certain that a peer-level conflict
a) will not be based on UAVs for long (my biggest concern about UAV-dependence of our forces), and
b) will be over one way or another pretty fast if it's not going to turn SO nasty that any conventional force tech will be nearly irrelevant anyway (the not-so-comforting corollary that would invalidate my concerns above)
-Styopa
This is so much pie-in-the-sky bullshit I can't even believe it. I hear about this kind of thing year after year, and it never happens.
This is DARPA, a company for whom "aim at the sky" is more of a directive rather than a metaphor. Some of there other work includes flying tanks, passive radar systems, stealth ships, onion routing, and wide area interconnected computer networks. Most of it doesn't work, of course... but when it does, we get something no one else would have bothered developing.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
1. The equipment may be ridiculously expensive (No problem: Around half the US government's budget goes to defence).
Dude, 30 years ago the idea of a hard drive with a "gigabyte" of capacity was something ridiculously expensive, taking up football-field sized buildings, and everyone thought it'd be a really dumb idea anyway; Tape would be better for storage. Now I can get 64GB of storage to fit on my index finger and it's only a fingernail's thickness. The argument of "it'll be ridiculously expensive" dies over a long enough time span.
It'll need to be such high (analog) bandwidth, it'll not comply with any spectrum or power regulations, anywhere.
Ding! We have a winner. Though, not for the exact reason you're thinking. It could in fact work, and even within certain power requirements. But it'll never get regulatory approval, and it has nothing to do with technical requirements, but the fact that (at least if we're talking about the United States) the people in charge are paid large amounts of money to maintain the status quo. Remember that price fixing scandal for digital TV when the FCC fucked up the transition so badly Congress had to intercede... three times? Yeah... what ever happened to them? Oh right... the FCC made billions, the corporations made billions... the taxpayers lost many billions, and... oh right: They were fined, uhh.. less than a penny on the dollar against their profits.
Every attempt to give the general public access to high speed digital communications for cheap has been blown out of the water faster than you can say "Republican in a bathroom stall at an airport."
#fuckbeta #iamslashdot #dicemustdie
This is actually a DARPA help wanted ad. And from description of the project sounds like a good job opportunity for some slashdoters.
here is the ad:
http://www.darpa.mil/NewsEvents/Releases/2012/12/14.aspx
and here is the proposers' day conference:
https://www.fbo.gov/index?s=opportunity&mode=form&id=e21984e31d49c3780966a53983daa4f6&tab=core&tabmode=list&=
The problem that was already addressed is the curving of earth, because it can be overcome with height. Let's sustain that increasing the altitude of your dishes will allow greater distance without the sphere's shape interfering, you still have all of the factors associated with those heights: weather, cost of getting there, service, general maintenance.
Maintenance: How easy is it to remove ice? Snow? What about the cost of maintaining the tower?
Service: What do you do when you can't communicate with the unit, and you've ruled out everything except the cable between the unit and it's nearest point of contact?
Cost: This is a broader issue than maintenance, because it allows for not owning the tower/building. Tower space is premium, building roof-tops are premium, labor to install, service, or repair is EXTRA premium. Not only do you need guys willing to climb 200+ feet, but they need to be technically capable. http://www.midweststeeplejacks.com/ charges no less than $250/hr.
Weather: Why don't you see point-to-point connections on towers that are 200ft up on towers? Because the bandwidth requires very high frequencies, and those frequencies are very susceptible to any movement caused by wind. I've seen a gentle breeze (on the ground) turn a wireless link from -45 dbi to -60. Let's not forget rain and snow.
The only good ways to mount an antenna or dish at a height, and ensure reliability, are with a very large antenna (think something with 3 or 4 legs and covering at least 400 feet^2), or a building.
An FM broadcast antenna is indeed directional, in the vertical plane. It flattens out the signal from a sphere so that most of the power is on a level plane. That's how an antenna creates gain. On the other axis it is most often omnidirectional. That 50KW is ERP (Effective Radiated Power), the transmitter is likely only putting out about 10KW.
Close but not quite. EIRP is where you start; with an idealized transmitter that radiates power equally in every direction. ERP is calculated based on the energy of the antenna's main lobe, which for an FM transmitter typically looks like a small circle and a long oval connected at the antenna. The difference in power between the EIRP model and signal strength in the main lobe of the antenna is the antenna's gain, which is where your ERP calculation comes from. A transmitter with an antenna having 6dB of gain means it can transmit at 10KW and have an equivalent signal strength (in the main lobe) to an ideal antenna radiating in all directions at 40KW.
#fuckbeta #iamslashdot #dicemustdie