Tag Archives: transmission

Superstorm Sandy Shook the Earth

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Storm-induced seismic vibes aren’t a newly recognized phenomenon. In 2005, ground motions triggered by Hurricane Katrina were picked up by seismometers in California. And even storms that remain far from land can trigger ground motions, Sufri and Koper note.

Because the strongest ground motions are typically created at or near a storm, researchers can track its progress using seismic data alone. That offers opportunities for scientists to delve through old data sets—especially those from the presatellite era—to look for signs of storms that might have been missed by earthbound observers, or to better estimate their paths and intensities, Sufri says.

via Superstorm Sandy Shook the Earth – ScienceNOW.

It amazes me how sensitive those seisometers must be.

Docsis 3.1 Targets 10-Gig Downstream

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ORLANDO — SCTE Cable-Tec Expo — The Docsis 3.1 platform will support capacities of at least 10Gbit/s downstream and 1Gbit/s upstream, a move that will certainly prolong the industry’s need to deploy fiber all the way to the home.

via Light Reading Cable – Cable – Docsis 3.1 Targets 10-Gig Downstream – Telecom News Analysis.

To hit its capacity targets, the cable industry wants to increase its spectral efficiency by about 50 percent. As expected, the new specs will do away with 6MHz- and 8MHz-wide channel spacing and instead use smaller (20KHz-to-50KHz-wide) orthogonal frequency division multiplexing (OFDM) subcarriers; these can be bonded inside a block spectrum that could end up being about 200MHz wide. (See Docsis 3.1 Will Change Cable’s Data Channels.)

The definition of ofdm from wiki.

Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for widebanddigital communication, whether wireless or over copper wires, used in applications such as digital television and audio broadcasting, DSLbroadband internet access, wireless networks, and 4G mobile communications.

And the primary advantage using ofdm is:

The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions (for example, attenuation of high frequencies in a long copper wire, narrowband interference and frequency-selective fading due to multipath) without complex equalization filters.  Channel equalization is simplified because OFDM may be viewed as using many slowly modulated narrowband signals rather than one rapidly modulated wideband signal.