World Record: Wireless Data Transmission at 100 Gbit/s | Hacker News Reader

World Record: Wireless Data Transmission at 100 Gbit/s

kit.edu

54 pointsdirktheman14 comments

Based on a quick read, it looks like this works only over relatively short distances and requires a direct line of sight between transmitter and receiver, so the main application of this technology will be bridging gaps in fiber optic networks.

Link to paper: http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nph... -- its contents are behind a paywall, but the abstract and several illustrations are free.

Yes, but they did achieve a transfer speed of 40 gigabit/second over a distance of about 1 kilometer, from one highrise to another. The line of sight could be a problem, though!

There are a lot of LoS wireless networks in use all over the place (at least in the US). They're only a small fraction of the wired networks, but they're still important links.

For example, the City of Melbourne (Florida) uses wireless links for intra-city WAN traffic. The cost analysis versus building a fiber network was laughable. Granted, you don't get the speed and latency of fiber, but even when they built in extra software (to provide LAN nodes for latency sensitive services), wireless came out ahead.

This development won't help with latency, but more throughput is always welcome.

The startup I'm currently at leases space from a broadcast network in Chicago; they're using LoS microwave to throw their HD content from the plant at the building up to their broadcast antenna atop the Sears Tower.

>Granted, you don't get the speed and latency of fiber

I get the speed but where do you lose the latency? LoS is the shortest path and fiber is slower than speed of light so I'd actually expect latency to be lower. Wall Street low latency trading is moving to microwave to exploit this:

http://www.wallstreetandtech.com/data-latency/low-latency-ma...

I just kind of assumed it would be worse than a fiber link. Most wireless networks suffer from poor latency, but I could see where a dedicated point-to-point network could be better optimized for latency when compared to something like WiFi.

What's even more mindboggling is that, through combining multiple data streams, wireless transfer speeds of over 1 terabit/second seem to be possible. However, what really blew my mind is that their total budget is just 2 million euros. Pocket change compared to the n-th cat pic sharing app that just got funded.

Depends on your bandwidth. For most real world applications, you're probably going to hit the Shannon limit at much lower data rates.

For example, with 1GHz of spectrum (a huge amount compared to WiFi (40MHz for 802.11n) or LTE (20MHz)), with an excellent 50dB signal to noise ratio, you can never move more than 16.61 gigabits per second.

True, but if I recall correctly spatial multiplexing can be used to increase channel capacity.

Using the same 50db SNR for WiFi at 40Mhz we get:

  ((40000000)*(log(1+100000)/log(2)))
  ans =  6.6439e+08

or 664Mbit/s, however, 802.11ac can achieve higher than that by using MIMO. I unfortunately don't know the formula for max channel capacity for multiple streams.

It doesn't seem like they are using this though in their experiment.

I guess I had recently heard of a 10gb wireless from Batelle (pdf) http://www.battelle.org/docs/battelle-invents/g_data_wave.pd... and looks like they are also working on a 100gb. I struggled to find ideas on how to use such a thing other than say live transmission of >10 10k resolution video streams over a couple of miles, or urban office backbones and such. The rain degrading the connection is a thing with it all.

For a comparison, as of 2 years ago, wired network records are over 1000 times that:

http://www.popsci.com/technology/article/2011-04/two-differe...

This is interesting, because it appears that they just took a 15 Tbps technology and used 7 of them at once to get 100 Tbps. As in, they could have used 70 of them at once and achieved 1 petabit per second.

I imagine that in either case, they're using multiple computers to do the transmitting and receiving.

I'm more impressed with the 40 Gbit/s over 1 KM (0.62 miles)

hello !!

Reply on news.ycombinator.com