Telecommunications is primarily divided up between wired and wireless
subtypes. Overall though, a basic telecommunication system consists of three
main parts that are always present in some form or another:
- A transmitter
that takes information and converts it to a signal.
- A transmission
medium, also called the "physical channel" that carries the
signal. An example of this is the "free space channel".
- A receiver that takes the signal from the
channel and converts it back into usable information for the recipient.
For example, in a radio broadcasting station the station's large power
amplifier is the transmitter; and the broadcasting antenna is the interface
between the power amplifier and the "free space channel". The free
space channel is the transmission medium; and the receiver's antenna is the
interface between the free space channel and the receiver. Next, the radio
receiver is the destination of the radio signal, and this is where it is
converted from electricity to sound for people to listen to.
Sometimes, telecommunication systems are "duplex" (two-way
systems) with a single box of electronics working as both the transmitter and a
receiver, or a transceiver. For example, a cellular telephone is a
transceiver. The transmission electronics and the receiver electronics within a
transceiver are actually quite independent of each other. This can be readily
explained by the fact that radio transmitters contain power amplifiers that
operate with electrical powers measured in watts or kilowatts, but radio
receivers deal with radio powers that are measured in the microwatts or nanowatts.
Hence, transceivers have to be carefully designed and built to isolate their
high-power circuitry and their low-power circuitry from each other, as to not
cause interference.
Telecommunication over fixed lines is called point-to-point communication
because it is between one transmitter and one receiver. Telecommunication
through radio broadcasts is called broadcast communication because it is
between one powerful transmitter and numerous low-power but sensitive radio
receivers.
Telecommunications in which multiple transmitters and multiple receivers
have been designed to cooperate and to share the same physical channel are
called multiplex systems. The sharing of physical channels using multiplexing
often gives very large reductions in costs. Multiplexed systems are laid out in
telecommunication networks, and the multiplexed signals are switched at nodes
through to the correct destination terminal receiver.
The team of computer scientists and electrical engineers has detailed one of
the first complete systems to encode, store and retrieve digital data using DNA
molecules, which can store information millions of times more compactly than
current archival technologies.
In one experiment outlined in a paper presented in April at the ACM
International Conference on Architectural Support for Programming Languages and
Operating Systems, the team successfully encoded digital data from four image
files into the nucleotide sequences of synthetic DNA snippets.
More significantly, they were also able to reverse that process --
retrieving the correct sequences from a larger pool of DNA and reconstructing
the images without losing a single byte of information.
The team has also encoded and retrieved data that authenticates archival
video files from the UW's Voices from the Rwanda Tribunal project that contain
interviews with judges, lawyers and other personnel from the Rwandan war crime
tribunal.
"Life has produced this fantastic molecule called DNA that efficiently
stores all kinds of information about your genes and how a living system works
-- it's very, very compact and very durable," said co-author Luis Ceze, UW
associate professor of computer science and engineering.
"We're essentially repurposing it to store digital data -- pictures,
videos, documents -- in a manageable way for hundreds or thousands of
years."
The digital universe -- all the data contained in our computer files,
historic archives, movies, photo collections and the exploding volume of
digital information collected by businesses and devices worldwide -- is
expected to hit 44 trillion gigabytes by 2020.
That's a tenfold increase compared to 2013, and will represent enough data
to fill more than six stacks of computer tablets stretching to the moon. While
not all of that information needs to be saved, the world is producing data
faster than the capacity to store it.
DNA molecules can store information many millions of times more densely than
existing technologies for digital storage -- flash drives, hard drives,
magnetic and optical media. Those systems also degrade after a few years or
decades, while DNA can reliably preserve information for centuries. DNA is best
suited for archival applications, rather than instances where files need to be
accessed immediately.
The team from the Molecular Information Systems Lab housed in the UW
Electrical Engineering Building, in close collaboration with Microsoft
Research, is developing a DNA-based storage system that it expects could
address the world's needs for archival storage.
First, the researchers developed a novel approach to convert the long
strings of ones and zeroes in digital data into the four basic building blocks
of DNA sequences -- adenine, guanine, cytosine and thymine.
"How you go from ones and zeroes to As, Gs, Cs and Ts really matters
because if you use a smart approach, you can make it very dense and you don't
get a lot of errors," said co-author Georg Seelig, a UW associate
professor of electrical engineering and of computer science and engineering.
"If you do it wrong, you get a lot of mistakes. If you more about
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