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In the past few years, researchers at Georgia Tech, MIT, Intel, and elsewhere have made great strides in developing millimeter-wave devices. Companies such as Intel have even started pushing for standards that could help develop interoperable technologies that operate at 60 gigahertz. And one company, Gigabeam, has rolled out products that can achieve around one gigabit per second using a point-to-point link over a few hundred meters.
Ridgway explains that using telecommunication lasers has two big advantages. First, they are high power, so the resulting millimeter wave is also of relatively high power. Second, the lasers have been engineered to be stable and dependable, producing a signal that doesn't fluctuate much compared with standard millimeter-wave sources.
Alan Crouch, director of the Communications Technology Lab at Intel, says that the Battelle work is further evidence that millimeter-wave technology could become increasingly important. "There's demand for more and more wireless communication solutions in this space," he says, adding that "there is strong industry interest."
But the research may be years away from being deployed in a product. Ridgway explains that, since the system has been put together from existing components, it's much larger than it ultimately needs to be. In addition, a property of the signal called polarization, which plays a role in encoding data, tends to drift during operation, which means that the system requires attention when running. But Ridgway hopes that, with some more engineering, these problems can be ironed out. "We'd like to get it to a point where you could just turn on and go," he says.
Small, low-power access points boost wireless speeds indoors and in busy areas.
There are some limitations that may be worked through but make me reserved. For starters it looks like this is unidirectional, which means it will largely be used for backbones. I think we are getting ahead of ourselves with images of a dish on every roof delivering 10Gbps dancing in our heads. Next, as far as I know the higher frequency = more easily blocked by physical matter such as trees, houses, etc. This is why 2.4ghz is still favored over 5ghz in spite of the 2.4 freq. being cluttered.
This sounds great, but I think the applications will still be very limited.
@runlevelfour You're definitely right about limitations. Since the signal is sent in a point-to-point manner, it's not the sort of wireless that could work as a cellular network. That said, there are plenty of applications where cutting the cord or fiber, even in direct line of sight, could be beneficial.
Higher frequencies do not allow for higher transfer rates because they "oscillate faster." This is simply not true at all. Hey, don't you guys teach Shannon's theorem over at MIT? It's from 1949 and it is a fundamental concept in communications technology. It is just as important with modern 10 gigabit wireless technology as it was in 1949. The limit of the bits that you can pack into any given amount of spectrum is based on the modulation rate, the noise floor, and the channel bandwidth. The 60 GHz and 100 GHz bands have more speed because they allow for huge (1GHz+) RF channel bandwidth. These high frequencies don't propagate well (they are absorbed by anything) so they aren't considered highly valuable. Thus, large chunks are given away.
How and what type of modulation are they performing on the laser beam? I'm assuming that they modulate the frequency on one beam to create a beat frequency that is in the 100 GHZ neighborhood.
So, I'm curious, and I'm hoping someone can clarify for me: Are they modulating the actual frequency of the beam (i.e. the color of the laser beam) or do they use a more conventional Pulse Width Modulation approach to achieve the resultant frequency? If it was PWM, wouldn't you have to Modulate somewhere the millimeter and above spectrum anyway in order to get the right beat frequency?
Also, as far as the 10GHZ signal being up-converted to 100GHZ, since we're talking about data transmission, wouldn't it be possible to just divide the data stream and multiplex into the 100GHZ spectrum? Which is theoretically cheaper? 10 TX pairs to get 100 gigabit bandwidth or one laser setup per TX point?
Using MMW & sub-MMW for line-of-sight communication purposes has been studied for quite some time, especially in context of inter-satellite. The high power requirements are needed to offset the atmospheric, precipitation, and other propagation losses and effects. If I remember correctly, there are four useful windows: 35, 94, 120, and 220 GHz. I'm glad to finally see some investment in this area.
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camdaddy09
38 Comments
Satellite communications?
I realize this is a huge leap forward but, what about using this instead of cell towers to run our portable devices? I do realize that the thing keeping cellphone satellites back is the slow connection speeds and all the trafic coming through it at one time. It would be awesome if we could live in a world where you were never out of touch!
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gupta
7 Comments
Not so new...
The guys at Bridgewave have been at it longer.
http://bridgewave.com/products/60ghz.cfm
Finding a market in the process, and weathering the market since year ~2000... not so easy.
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adfadfa
1 Comment
Re: Satellite communications?
There is hope that it will all be able to be used by the same tower...ever heard of skype telephones??
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