10Gbps Wireless Transfers 173
Erasei writes "NTT Science and Core Technology Laboratory Group has developed a wireless communications that is capable of transmitting data at speeds of up to 10Gbps. In order to achieve such high data transmission speeds, the system uses the as-yet-unused 120GHz frequency band. The actual bandwidth the system uses is 17GHz, and the method of modulation employed is amplitude shift keying."
FP (Score:1, Interesting)
Getting faster (Score:5, Funny)
Re:Getting faster (Score:2, Informative)
Regards, Adam.
Re:Getting faster (Score:2)
Re:Getting faster (Score:5, Funny)
THIS JUST IN! (Score:5, Funny)
Re:THIS JUST IN! (Score:5, Funny)
OT: Re: THIS JUST IN! (Score:1)
Simply outrageous.
Email me if you ever do.
Re:THIS JUST IN! (Score:1)
It's true (Score:2, Informative)
What range? (Score:3, Informative)
Not sure what this would be usefull for..
Re:What range? (Score:1)
And what's to stop them from using an omnidirectional antenna?
Regards, Adam.
Re:What range? (Score:5, Interesting)
As for omnidirectional, that would lower your effective point to point power further.
At these freq's it could only be useful for point-to-point comms.
I wonder why they did not just leave it all optical.
Re:What range? (Score:4, Informative)
"In the laboratory, a 10m range for the system has been confirmed, but NTT is expecting to try and extend the range to 100m."
No, I saw the freq. (Score:2, Insightful)
Back to my original point, I see no way for this to be useful.. This will never leave the lab until you get it down to a few chips!
The 17GHz bandwidth of the signal is quite impressive, though.
Isn't Less More? (Score:3, Insightful)
Failing the "more data" point, I'd like to see a lot less bandwidth used, just to accomodate the artificial "crowding" of the spectrum. At this point, 10Gbps isn't very useful yet.
I mean, look, people! You're talking about 1.7 GHz/bit. To put that in comparison, think of extreme environments. If a deep-space probe developer only had a 17Hz signal, would you want to get only 1 bit per second, instead of the theoretically possible 8 bits per second? (IIRC, the theoretical limit for data transfer on a specific RF wavelength is freq/2. Any more, and you can't tell signal from noise without something as redundant as a UPS address stamp.)
I know this sounds like a "640k is all you'll need"-type-argument, but why not use a smaller bandwidth, and allow for multiple independant channels? If you need additional data transfer, you could use channel bonding.
This'll especially help wireless providers, who have to relay their signal from tower to tower without hitting the tower-after-the-next with a poorer signal. (Signals will travel beyond the horizon, but not very reliably.) Currently, they use polarization of their signal.
Re:Isn't Less More? (Score:2)
Re:Isn't Less More? (Score:2)
False. It's actually dependant on bandwidth and signal-to-noise ratio. See Shannon's Law [google.com].
Re:What range? (Score:2, Insightful)
I wonder how we could do that...oh! I know!
High speed data communications in previously unused (and unregulated) spectrum. Anyway, how do you regulate light.
I know, you may be wondering, won't this have serious side effects for people.
Don't worry we'll test it on engineers and programmers.
Re:What range? (Score:5, Funny)
My current device uses the 560nm-800nm electromagentic spectrum. And while it can send a large volume of data quickly, my receiving unit processes the data, but most it is lost in storage. If only the process wasn't so lossy!
Can anyone recommend any upgrades? I am still using the orginal neural network that came with this model...
(too subtle?)
Re:What range? (Score:1)
If you give me a grant of, say, around 50-60 billion dollars(adjustable to inflation) annually over the next, say 70 years I guanantee will build you a working model. Note this is not an actual, legally binding guarantee.
Re:What range? (Score:1)
Re:What range? (Score:4, Informative)
Actually, 120 GHz is a fully regulated part of the radio spectrum. The Powers That Be regulate it (and assign users) up to 300 GHz. There is increasing interest in this part of the spectrum, partly because the lower frequencies are getting crowded in some parts of the world, and because atmosphereic attenuation (which is high at these frequencies) makes frequency reuse a lot easier. The military are interested too, since that same attenuation makes it hard for unfriendlies to listen in on tacitcal communications. Unless they're right in the middle of the battle, in which case they have other things to worry about...
Anything beyond 300 GHz is terra incognita - electronic techniques become impractical, and optical techniques don't work well until you go lots higher in frequency. You can buy infrared data links that will shoot data across town, and they are not regulated (as radios) in any way. They require laser certification only.
...laura
Re:What range? (Score:3, Funny)
Re:What range? (Score:3, Informative)
Thus at very high frequencies you have to have exponentially more power to transmit the same distance, or you have to have an equivalently more directional antenna.
This fact is one of the reasons that spectrum is so valuable. The higher the frequency, the more costly and less practical it is to use it for non-stationary applications. In addition, as you get to higher frequencies you run into more problems with attenuation due to atmosphere, rain, walls, earth, etc. In addition to that, transmitters are significantly less power efficient at higher frequencies.
Add all that up and you have several exponentials retarding advances into higher frequencies.
Any encryption challenges at that speed? (Score:5, Interesting)
I'm not thinking so much of a peer-to-peer or client/server setup where there's a networking handshake, but more along the lines of a broadcast data stream meant for everyone (or maybe just a few certain someones) to pick up.
Re:Any encryption challenges at that speed? (Score:3, Interesting)
Re:Any encryption challenges at that speed? (Score:1)
Re:Any encryption challenges at that speed? (Score:4, Interesting)
Re:Any encryption challenges at that speed? (Score:1)
Re:Any encryption challenges at that speed? (Score:2)
I don't think anyone is going to be broadcasting data on the 120GHz band, though. At these frequencies radio is strictly line-of-sight. Encryption and key management is relatively simple in a point-to-point application.
it will probably be slashdotted, not a major site (Score:5, Informative)
October 18, 2002 (TOKYO) -- NTT Science and Core Technology Laboratory Group has developed a wireless communications system using the 120GHz band.
The system, which is capable of transmitting data at speeds of up to 10Gbps, was displayed at the "NTT R&D Forum 2002" event held Oct. 11 in Atsugi.
The new system is four times as fast as the 2.5Gbps wireless system NTT put on show at the same event in 2001. This is the first time the laboratory experimented with a 10Gbps wireless system (photo). There are many potential uses for such a high-speed wireless technology, such as for 10Gbps wireless Ethernet links or for radio links between different buildings where a high volume of data has to be sent to and fro. NTT plans to announce the new system at the "Asia-Pacific Microwave Conference" (APMC) to be held in Kyoto in November.
In order to achieve such high data transmission speeds, the system uses the as-yet-unused 120GHz frequency band. The actual bandwidth the system uses is 17GHz, and the method of modulation employed is amplitude shift keying (ASK), the simplest method of amplitude modulation for digital signals. According to an NTT source, by modifying the modulation method, the throughput rate will be improved.
NTT also used optical communications technology to make the 120GHz system possible. A 120GHz optical pulse signal is generated, and then undergoes amplitude modulation. After modulation, the signal is picked up by a special photodiode capable of responding with the high-speed signal. The output from the photodiode is then transmitted as a wireless signal. The special photodiode used was developed with NTT's own technology, and can handle optical inputs of up to 300GHz.
The main difference between last year's system and the new one is that the receiver frequency detection circuitry has been redesigned, meaning that the receiver can detect signals over a wider bandwidth, and thus the system can operate at faster speeds. The new detection circuit can receive signals from an 8.5GHz band at maximum. Because the system employs two detection circuits working in tandem, the finished system realizes more than a 17GHz band.
At "NTT R&D Forum 2002," the system was shown transmitting non-compressed HDTV-quality (1.5Gbps) video data. In order to extend the range of the transmission, a 20cm-diameter lens was used to focus the beam. In the laboratory, a 10m range for the system has been confirmed, but NTT is expecting to try and extend the range to 100m.
send me that file.... (Score:3, Interesting)
Yeah, like 1.5 terabytes a day!
Re:it will probably be slashdotted, not a major si (Score:4, Funny)
Refracting radio waves through a lens? (Score:2, Interesting)
OK... keep us posted (Score:5, Insightful)
From a scientific standpoint, this is somewhat interesting. I don't see it being news, however, until they seriosuly decrease the size of the transmitters and/or increase the range. The transmitters look to be about the size of a shoebox, which is great for building-to-building, but let us know when they actually bump up the range to say... building-to-building distances.
Re:OK... keep us posted (Score:2)
and from the article:
"In the laboratory, a 10m range for the system has been confirmed, but NTT is expecting to try and extend the range to 100m."
Bamn- there's your MAN infrastructure.
Fast Wireless (Score:4, Funny)
wave propagation similar to infrared (Score:5, Informative)
Re:wave propagation similar to infrared (Score:2, Interesting)
Re:wave propagation similar to infrared (Score:5, Informative)
Millimeter wave imaging can operate in this frequency, because there's an atmospheric window (read: longer range) around there, and because most non-conducting "solid" object appear translucent at that wavelength.
So we would expect some penetration through walls. Especially the cheap drywall they use where I work
Rain will reduce the range/bandwidth, but it should go through dust, smoke, L.A. fog, etc. pretty well.
Here, take this (Score:5, Funny)
And is that a run-on? Sheesh. Critics.
Re:Here, take this (Score:2, Funny)
10 Gigs a second, eh? (Score:3, Funny)
Did some similar research... (Score:1, Troll)
One of my favorite areas of study in this filed was the derivation of optimum receiver principles (including intersymbol interferences and equalization). You really can't appreciate a cellular phone and its chat/texting abilities until you understand just how hard it is to ensure lossless cellular communication between two carriers.
The modulation and coding for fading wireless channels, as well as spread spectrum communication analysis is rather tedius in my opinion, but overall it didn't taint my feeling that wireless is where the future is going and that what I was studying had some actual real-world application to it.
All too often academia is just going thru the motions without delving into the real trials/tribulations/concerns of modern-day corporate research.
range, penetration and cost? (Score:5, Interesting)
10 meters would limit its usefulness, but 100 meters would make this very useful. Hopefully, this has a useful range.
Could someone answer the question about how easily this frequency would pass through common substances, like walls?
Also, there was no mention of weather they would seek to license their technology to make this widely available or just make this a very expensive specialized niche product.
Re:range, penetration and cost? (Score:2, Interesting)
Well maybe very very thin walls
Think of it as a laser (Score:3, Informative)
Re:range, penetration and cost? (Score:2, Interesting)
Line of Sight? (Score:1)
That is the frequency the aliens use. But I confuse them with aluminum foil!
"I'll handle this
-Homer Simpson
Not for the office (Score:5, Interesting)
You'd never see anything like this in a home or office, as it couldn't penetrate a sheet of paper, let alone a wall of any type. I suppose it could penetrate if you put enough power into it, but then it would need enough power to melt through the wall before the communication could begin.
Re:Not for the office (Score:3, Funny)
Mad, mad props to the RF guys on this one (Score:5, Interesting)
Open up an 802.11 card for instance--these work at about 1/60th of that frequency--and look at the traces for an idea. It's not just what components are connected together--it's the layout of the traces that define most of the circuit. Inductors are little squiggles, a resistor is the thinning of a trace, etc., all of which is highly dependent on frequency.
In other words, these guys are pretty slick and you just have to bow to them.
Doesn't anyone read the article before posting?!? (Score:2, Informative)
Re:Doesn't anyone read the article before posting? (Score:1)
The optical signal is modulated, then transmitted on 150Ghz-band RF signal.
Re:Doesn't anyone read the article before posting? (Score:1)
There is no difference between 'optical' and 'rf'
An electromagnetic wave is an electromagnetic wave.
There are just different frequencies
Re:Doesn't anyone read the article before posting? (Score:3, Informative)
Yes, we do. Do you? It uses optical means to generate the 120 GHz RF inside each unit, NOT BETWEEN THE BOXES.
Obligatory nit: Optical is RF. Just really high in frequency (THz).
Distance (Score:3, Interesting)
Has anyone looked at the prototype they have in the picture? The transmitter and receiver are on the same table. Sure, I can understand 10gbps per sec over a few feet. They don't even know how this new technology will stand up in normal conditions. There is no way currently this will be used in mainstream. I don't know of anyone that is willing to sit within 10m of the transmitter to receive there wireless connection. I know this will be improved, but the distance will have to grow by leaps and bounds.
Yea, trasmitting 10gbps is nice, but currently what use is it if you can't go within a few feet of the transmitter?
Re:Distance (Score:2, Insightful)
You must learn to crawl before you can run.
Re:Distance (Score:1)
Re:Distance (Score:4, Funny)
Wow, how'd they get the transmission rate to accelerate like that?
Obligatory Ronja link (Score:2, Informative)
Also known as Fast Ronja [jikos.cz]. Cool as hell though.
Speed is good, but (Score:2, Insightful)
We develop wireless applications, and we'd sell probably twice as many if the hardware was secure, but sales would not go up at all if the speed of the networks was faster.
Re:Speed is good, but (Score:1)
Re:Speed is good, but (Score:2, Informative)
How's the view from that Ivory tower? (Score:2)
Nobody refused to buy an HP/UX box, or a Sun E2k because their NICs were'nt 'secure', and nobody ripped out all of their 10Mb Ethernet infrasructure for the cause of security either.
What caused organizations to pull out all of their old NICs though? Speed. It will always be speed. What kind of world do you live in where you think that 2x as many wireless nodes would be sold if they were 'more secure'? I sell them for a living, and nobody I work with is worried about security. I'd love it if they were so I could sell our IPSEC solution to them as well, but...
Sometimes I'm amazed at how out of touch with the real world us geek types can get...
UWB - A lesser known wireless method (Score:1)
Streaming "open source" video (Score:2)
Wasn't this already posted today? (Score:1)
drilling through glass [slashdot.org] part.
they should be making it longer range (Score:1)
What's Pikachu have to do with this? (Score:4, Funny)
Does his thunderbolt attack provide the jiggawatts of power needed?
Can we hit 100Gbps if he evolves into Raichu?
Or, most importantly, will this technology help me catch 'em all?
It's Gbit/s, not Gbps -- And it's a big problem! (Score:3, Insightful)
Journalists are fond of using dumbed-down abreviations such as Gbps or other acronyms. But I encourage technical writers to use the correct term, which is Gbit/s. Just as Mbit/s, Kbit/s.
There is something weird with computer science. People in this discipline badly need a common linguo because the field is evolving so fast. And yet, most CS practitionners couldn't be bothered to use the generally accepted vocabulary or abbreviations to describe their domain's problems. They invent their own, or incorrectly reuse existing jargon swiped from other disciplines.
Even worse, each branch of CS reuses general vague terms and overloads them with a different meaning. What's a "server"? What's a "page"? Depends who's talking.
As a result, CS is full of islands of disconnected knowledge and of specialists that cannot communicate with each other. Ever tried to have an OO programmer and a database admin talk to each other?
Mathematicians don't speak each other's linguo. But they carefully avoid using overlapping terms to define different things. That's what we should aim to do.
CS will keep being a cottage industry and a craftman discipline akin to voodoo, with cancelled project when wizardry fails, as long as all CS won't agree to speak a common language. Or at least a language where precision removes the overlapping meaning.
Granted, a precise vocabulary will not cure all the ills of CS. It not a sufficient condition for clear communication. But it's one of the necessary conditions.
So do your part. Write Gbit/s, not GBPS or other atrocities.
Re:It's Gbit/s, not Gbps -- And it's a big problem (Score:1, Funny)
It should be kbit/s not Kbit/s. Kilo is abbreviated 'k' to avoid confusion with 'K' for Kelvin.
I encourage you to use the correct term.
Cheers mate.
Re:It's Gbit/s, not Gbps -- And it's a big problem (Score:2)
I always like the people who were kind enough to be precise, where
so that Gbps and GBps are different.And while we're on the subject, of course, where
where it's even more helpful to put a "2" subscript on the G to indicate 2**30 instead of 10**9.It's usually too much to hope for from most news sources. Usually only academic papers care enough to be precise with their nomenclature.
Frequency reliability (Score:3, Interesting)
My question is, how much would a heavy rain/hail/snow shower affect a long range link at these high frequencies?
Re:Frequency reliability (Score:1)
again, new tech but when will it be available? (Score:4, Insightful)
the article mentioned that this new wireless system uses a yet un-used 120GHz frequency. i personally feel that this can -both- be a disadvantage and advantage to its entry into the mainstream market. reason being, due to the 120GHz frequency being unused, widespread adoption might be made easier without any regulations but then again, that same lack of regulations would make it hard to regulate and control, and it might be open to abuses by users with malicious intent. worst still, all our beloved governments or telecommunication companies (for some countries, the above two are one and the same for all intents and purposes) will seize the opportunity to reap a handsome profit and end up killing the potential this product might have had in the market.
another factor, and perhaps the -most- important factor to consider is cost. the system may be cheap to built and maybe it didn't cost that much to develop, but we all know capitalism isn't about selling products at a price that indicates its real worth, capabalities, and cost of manufacture or R&D. rather, market demand or greedy corporate figures play an important part, along with sleazy marketing methods that target the ill-informed but rich people, who buy into meaningless numbers generated by the afore-mentioned marketing folks. the success or failure depends on how well the balance, between reaping the most profits and at the same time allowing growth, expansion and demand of the product to propagate is upheld by those corporate capitalist (and usually greedy) folks.
lastly, but not as importantly as the above factor, is whether the four times increase in speed is really needed, or is it on par with a 2.0GHz pentium 4, in that both only have impressive numbers to show off, which represent little of any real-world increase or -need- for performance for most mainstream users. but then again, i've just made a moot point haven't i? the sad reality is that the actual technology or the need for it isn't what sells. its how well its marketed (read: exaggerated and made pretty with big numbers) that really counts, ain't it?
if anyone feels like modding me down, go right ahead. i just had to get that off my mind. i just can't help being a little more and more pessimistic each time a promise of some new-fangled gadget makes headlines on slashdot, only to make headlines a year or two later when it flops over on its belly.
Re:again, new tech but when will it be available? (Score:1)
now the 120GHz gizmo wont transmit very far (unless you have wireless laser-like (maser!) beams that go pt-pt) but that could result in low/no interference for others and a 10GigEthernet all to myself and my gadgets within 10 feet.
on a related note, TeraHz (light) carriers are being used to transmit 10Gbps x many wavelengths (colors) today (see Lightpointe, Zyoptics,...) but are finding limited use
-dharmic whore
So why is IRDA so slow? (Score:5, Insightful)
Re:So why is IRDA so slow? (Score:4, Informative)
The problem is twofold.
On one side, there is large demand for some things to remain backards compatible with legacy devices like VCRs and Stereos, which is much easier to do when your standard rate of transmission is lower.
However, with that said, I believe the real "problem" with IRDA lies in on the error detection and correction side of things. The same is true of TCP/IP. It could be significantly faster (ala UDP) if we did not want guarenteed delivery.
IRDA is significantly slower than things like microwave PTP because they leave room in the modulation timing for not quite perfectly aligned transmissions. Whilst motor skills in the human hand allow for the precision neccessary to enact a successful transmission, more often than not there will be either vertical or latteral movement in the outer extremities of the device (usually the end with the transmitting diode on it) which would cause transmissions with faster modulation to fail... as it is, the millisecond sync loss is (usually) able to be recovered from my simply resending the data sent since the last acknowledgement packet.
In short, yes, you could do it, but you would have to hold those things *REALLY* steady, maybe to the point of having to set them on a solid surface whenever you wanted them to communicate... since the manufacturers are catering to the general unwashed masses, they create the device to be idiot proof ala very slow transmission speeds and large error windows.
Hope this helps.
Can the guys in Africa use it? (Score:3, Informative)
Re:Can the guys in Africa use it? (Score:3, Interesting)
Re:Can the guys in Africa use it? (Score:1)
Re:Can the guys in Africa use it? (Score:3, Interesting)
But there is no rule that says antennas have to be any large fraction of a wavelength. A magnetic or electical antenna can be any size and have the same capture area as a dipole. This is because antennae do not have to be resonant to work - and a non-resonant antenna can be just as efficient as a resonant one, if you have a high efficiency circuit to tune out the reactance which results from the lack of resonance. This is one of the things an "antenna tuner" - familiar to ham radio operators does (the other is to transform the real portion of the impedance to a standard 50 ohms). However, it is hard to make efficient very tiny antennas. This is why these ELF systems have to use such high power.
HOWEVER, on a submarine, the resonant wavelength of a trailing wire antenna is *much* lower, because the speed of propagation in the waveguide formed by the antenna, insulation and salt water is much lower than the speed of light. Thus these antennas need only be a few hundred or thousand meters long to be reasonably efficient.
As an aside, my father invented this antenna in his PhD thesis about 50 years ago.
Re:Can the guys in Africa use it? (Score:2)
latency and speed issues. (Score:3)
Big deal. (Score:1)
This is completely boring, and useless to us home users. I can get 10Gbps with a $40 helium-neon laser.
For goodness sakes! (Score:2, Insightful)
But! Use your imagination here! Think of the posibilities - we're talking about a fast data transfer rate over short distances. Yeah 10m for now and with perhaps 100m in the future (building to building?) and what then? 1000m. Progress takes time.
And yes lasers can be used with high bandwidth (although you'll be lucky to make a photodiode with that good a bandwidth (~8.6GHz) - the only way I know of doing this is to use a broad resonant photodiode and this needs RF modulation and demodulation to make a useful signal - might be interesting to find out more about the "special" photodetector they developed) but higher frequency should be less susceptable to atmospheric noise and detection noise. Pro's and con's - might not be useful now but give it a couple of years and then we'll see.
Re:For goodness sakes! (Score:1)
something old in here (Score:3)
The article being low on content no explanation for ASK other than its simplicity. Isn't this method very susceptible to interference and noise ? Could this performance be achieved with MSK or QPSK ?
heh (Score:2)
Its land is mostly mountainous, and its chief export is beans.
Is 120 GHz even regulated? (Score:2, Insightful)
Does that mean that an unlicensed 200 GHz transmitter would be legal?
Film @ 11 (Score:1)
Silicon Valley, CA (AP)
This morning, Acme Semiconductor (NASDAQ: ACME) announced the unveiling of their new 15Ghz processors, dubbed JackHammer. Company officials displayed a hands-off demo of Quake 3, which reported a sustained frame rate of over 234,545 frames per second, an astonishing feat. A top-of-the-line 2.6Ghz Intel Pentium 4 produces numbers in the mid hundreds, depending on the established screen resolution.
Company officials told reporters that the Internet is faster on computers based upon the JackHammer. Photoshop filters take dramatically less time to render as well, they added.
Acme says it plans on shipping the processor mid to late 2005.
Stock Ticker - All prices delayed 20 minutes
Acme Semiconductor (ACME) || 14 1/4 || +5 7/8
Gosh (Score:2)
Lame (Score:2)
Society has also developed a grammaticals that communicate helps. Try it, you should.
1.5 Gigs per second? Average vs max? (Score:2)
Is this right? Did I see Gigabit per second? I assume that it's actually 1.5Mbps?
Regardless, am I the only one who gets scared when a company says "max" or "up to." How about a average/nominal rating, so that we can see what most users get on a normal day, as opposed to every-second-sunday-when-the-moon-is-full. On a lot of devices, max rating is crap, as it rarely indicates the transfer speed achieved in most cases.
Re:1.5 Gigs per second? Average vs max? (Score:2)
What you receive on HD television sets is this signal compressed using MPEG-2 down to 19.34 Mbps. And yes, in scenes with lots of independently moving things, there are visible artifacts.
Reed-Solomon and Trellis coding are added to provide some forward error correction. This increases the transmission bandwidth to 32.38 Mbps.
In the US, the 32.38 Mbps signal is transmitted using 8VSB (vestigial sideband) modulation, 3 bits per symbol at a rate of 10.76 Msps, Nyquist filtered to take up 5.38 MHz, which fits into a 6 MHz television channel.
120GHz unused? (Score:3, Informative)
AOL's new slogan: "You've got cancer!" (Score:2, Funny)
Re:why just now? (Score:5, Informative)
You guessed wrong. The range goes down as the frequency goes up. The higher the frequency, the more the radiation behaves like light, which is really just terahertz radio. As you get higher and higher frequencies, walls and such become more and more opaque to the signals. Until eventually they won't travel thru the walls at all, just like light.
If you want long range, you need lower frequencies. If you want to send a signal across the ocean, you need KHz radio waves (short wave radio). If you want to send a signal around the state you need AM radio at ~1MHz. If you want to send your signal around a city you can use FM at ~100MHz. By the time you get up to 2.4GHz you can only send your signal across a few rooms. Yes, I know I'm simplifying the differences in transmission power. But a short wave ham can reach across the world with less power than an AM station uses to cover a state, and the AM station uses less power still than the FM station which only covers a city or so.
Now, point to point is a whole different story. If you have direct line of sight you can send extremely high frequencies across significant distances. But the curvature of the Earth prevents you from sending stuff too far. Not to mention buildings and other obstructions.