Wireless 10 gigabits/sec data transfer

swedub writes "Lucent Technologies announced a breakthrough technology that eventually will enable business customers and service providers to transmit up to 10 gigabits per second (Gb/s) of information between locations through the air. " They are calling it WaveStar OpticAir. Global Crossing will be doing field testing this December already. This is the first system to actually use Bell Labs dense wave division multiplexing-can I get coverage in my area? But the encryption issues will be interesting, methinks.

Comments

Dense wave division multiplexing

[Omnibus]

GTE/BBN uses dense wave division multiplexing in their new GNI (Global Network Infrastructure). They got some nice OC192(10gbit) running all over (17,000 miles worth) and is already operational in several major markets. Lucent may be the first to use it wireless, but not the first to ever use it.

asinus sum et eo superbio

Re:Aligning that thing has got to be a problem

[Christopher Thomas]

The idea is pretty cool, but if you are transmiting several differnt frequencies at once will you not also need several emiters for each frequency and what happens if one of them gets out of alignment.

That depends on the modulation and mixing schemes that they use. By the time the carrier reaches the output, it's been multiplexed on to one beam, so lining up several emitters shouldn't be necessary.

OTOH, the transmitting and receiving mirrors will have to be aligned very precisely. There are a few ways to do this (even ways to do this automatically). Solving this is picky but not intrinsically difficult.

Come to think of it with that much band width the television / movie bizz has got to be excited. This has got to be cheaper than a satalite uplink and if there is a remote even within the usable range of this tech all they have to do is set up and shoot the video down it.

It would probably wind up being more expensive than satellite for TV broadcasting, actually, because TV is _broadcasting_ - using one (espensive) satellite to send data to many, many homes. The cost of the satellite is amortized over the number of viewers that it serves. A laser link, OTOH, only serves one user.

Where it would be more useful is in transmission of TV data from the master station to other distributing stations, but they already have microwave links in place for this (that's what all of those towers in the countryside with dishes and ariels on them do, among other things). Lasers would give higher bandwidth, but how many cable channels do they want to transmit?

What is the efective range of this anyway?

That depends on several things, but a previous poster said single-digit kilometres (or miles, if you prefer). This sounds reasonable. Haze in the air will scatter the beam after a while even in clear weather.

10 Gb, cool but limited

[jabber]

As another poster already noted, it's 10Gb weather permitting.

Also, it's a line-of-sight technology. I, for one, can't imagine this being used effectively for much more than spanning roadways and other public right-of-way restrictions without the legal hassle of an easement. Maybe jumping over a small river or such, but the morning fog, or the heat rising off the rooftops would just shoot your network to hell... ;)

Cost-wise, I doubt that this will ever be more affordable than traditional fiber. The endpoint hardware has to be at least as expensive, and the cost of fiber vs. the power needed to push light through the air is a major argument in favor of glass/plastic.

My 0.02 euro

yeah right.

[Skinka]

ping slashdot.org
>Request timed out.
>Request timed out.
>Request timed out.
>Request timed out.

"Oh shit, it's raining again!"

Really need to know the link budget

[Zoinks]

1) With regard to link reliability, we really need to see the link budget and the % availability they expect to achieve at 5 km. And just because it's raining, snowing or foggy doesn't mean the system is useless. Attenuation is not binary, and athough the link may go away at 5 km, it still may be useful at 500 m, because there's 20 dB more power in the link budget. I can imagine a semi-permanent link between buildings in NYC, for instance, that would expect and get 99.9% availability with this sort of link, and that might be just fine.

Birds are not so much a problem because if it's important, a TCP-like net connection is being used, and retransmissions will occur. Now a whole flock of birds, well...

2) Encryption? Well, it is hard to intercept because you'd have to be in the line-of-sight. Now if you're between the Tx and Rx, you'd probably have a good intercept, but you might ruin the link for the legit user. If you were behind the legit Rx, then that receiver would be blocking you, and you as well might be out of range for the link.

Still, if it's important, the user(s) that need encryption will do so as necessary on their connection(s) only.

3) No good for anything but line-of-sight (LOS)? This is still a big market for data carriers. There's bandwidth all over the place between 2 GHz up to 38 GHz for point-to-point use, and these pretty much have to be LOS-only. At around 28 GHz, there's LMDS, which is point-to-multipoint; still, it's LOS-only (in spite of what some might say).

This laser solution is clearly LOS-only, and will require proper aiming and all that at each end. And, it isn't very mobile, but Navy ships could certainly afford the required autotrack mechanism to make this useful even with gentle rocking of the ship.

Yes, I do this for a living, only at RF.

Possible applications

[Doco]

Anyone who has used a line-of-sight optical system for doing a T1 or something similar knows that this won't work worth crap in a lot of typical outdoor situations.

I see a couple of good applications.

1) Get the bandwidth up today while you get the trencher out to bury your fiber.

2) Replace the bandwidth today after somebody else cut through your cable trenching in their fiber ;-)

3) Use it indoors. Large convention centers could use a couple of these puppies to move lots of data around where fiber runs might not be pratical. Also think of Boeing's assembly plant. VERY large building with pretty decent sight lines without weather problems.

In general though - this is only going to be useful to a far smaller number of people than would use a traditional fibered system.

Visible Microwave

[pspeed]

Ok, I'm going to geek out here for a second...

It sounds like they intend to use this like point to point microwave, but in areas where microwave isn't feasible. This is becoming more and more of an issue with wireless local loop technology being the current vogue.

The problems with microwaves is that they scatter. Not only do you have to worry about the beam getting to the other end but you also have to worry about all of the reflected signal that will interfere with both ends and any other microwave sites. Plus there is the bleeding of signal out the back... the antenna patterns can be fairly complex and interference analysis is a very big business. Some would argue that the wireless local loop and point to multi-point markets have yet to be adequately addressed. The engineering can get very complicated. Especially if you are talking about small-scale dense areas like campuses and office complexes.

Also, the equipment for microwave is likely to be more of a hassle. If you aren't familiar with it there is a lot more to it than you might think. Compressors to keep the waveguides empty, etc.. (Fiber makes a pretty good waveguide for light. :) )

re: Weather. Light is highly attenuated by water droplets in the air but so are microwaves. This is all part of current reliability analysis when designing microwave links. There are known ways of limiting the affects of this and they might apply to light as well.

It would be interesting to have a reliability/attenuation comparison between microwave beams and light. If only I were a microwave engineer instead of the guy that writes some of their software... I might have more to say.