Bangor University Scientists Aim for 40Gb/sec Broadband Speeds
November 7, 2012 11:02 AM
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Super fast networking gear promises 2000 times faster downloads
2000 times faster downloads with little extra cost sounds pretty darn good
A team of researchers from Bangor University in the UK believes that they can create broadband speeds about 2000 times faster than we have today without a massive increase in costs. The team has managed to reach speeds of 20 GB of data downloaded every second. With that data throughput, you could download a full-length HD movie in about 10 seconds.
The team is now involved in a three-year project with the goal of making the technology commercially viable. The technology the researchers have developed uses fiber-optic cable. The problem with fiber-optic networks is that as the length of the cable increases, errors become more common in an effect known as dispersion.
While many in the industry have been investigating simply adding more physical fiber-optic strands inside cables to allow for the carrying of more data, increasing the size of fiber-optic cable gets expensive.
"The trouble is, that can all cost a lot of money," said Dr Roger Giddings, one of the team running the Ocean project in north Wales. "So the focus for the Ocean project is really to find out if we can do it in a cost-effective way, and is it a viable way of doing it in a commercial setting?
The method the researchers have devised to be able to send more data without introducing errors down a fiber-optic strand is called Optical Orthogonal Frequency Division Multiplexing, or OOFDM. The key breakthrough in the technology was the development of a piece of electronics that can encode and decode optical signals on the fly.
So far, the team has been able to reach data speeds of 20 Gb per second, but they believe they can reach speeds as high as 40 Gb per second. The team of researchers is also working with major industry partners, including Fujitsu, the Fraunhofer Heinrich Hertz Institute, Finisar Israel, and VPIsystems.
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RE: ofdm isn't new...
11/7/2012 4:51:52 PM
Frequency or wavelength division multiplexing are old concepts.
This is different. In frequency division multiplexing, you just assign one transmission to one frequency. Adam gets 100 MHz, Bob gets 101 MHz, Charlie gets 102 MHz. So each person gets one 1 MHz band.
frequency division multiplexing, multiple transmissions occur simultaneously
at the same frequencies
. Each individual transmission uses a orthogonal set of frequencies though, so even if transmissions overlap you can back out which transmitted what.
e.g. Adam gets 100 and 101 MHz. Bob gets 101 and 102 MHz. Charlie gets 100 and 102 MHz.
If Adam and Bob transmit a 1 at the same time, you see:
Where as if Bob and Charlie transmit a 1 at the same time, you see:
And if Adam and Charlie transmit at the same time you see:
Based on the signal strengths, the receiver can then figure out who transmitted what. Obviously it gets more complex as you increase the number of simultaneous transmissions and frequency bands, but you get the idea.
The beauty of orthogonal multiplexing is that you don't have to split up your bandwidth into n equal slices for n users. You can over-commit the bandwidth you give to each user. The maximum bandwidth available to each user ends up limited by the noise floor. If all three people are transmitting at the same time, then the noise floor increases, and each person's transmission is limited to 1 MHz of bandwidth (1/3rd of the 3 MHz). OTOH if two of them are transmitting, they effectively get 1.5 MHz each. And if only one of them is transmitting, they get a full 2 MHz (that's a limitation of my simplified example - in more complex coding, the lone transmission would get closer to having all 3 MHz bandwidth to itself).
So whereas in FDM you're limited to your small pre-allocated bandwidth, in OFDM the bandwidth you have available scales automatically depending on how many others are transmitting. Lots of people transmitting and your bandwidth is pretty much the same as FDM. But if fewer people are transmitting, you get more bandwidth. Potentially you could use
the bandwidth available if nobody else is using it.
CDMA does the same thing except using orthogonal codes, which is why it wiped the floor with GSM when it came to data service. (GSM used TDMA, or timeslices instead of frequency slices. It scaled so badly in bandwidth that they had to add CDMA data service to the GSM spec. If you use HSPA+ on AT&T or T-Mobile, you're using wideband CDMA.)
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