Bandwidth: From analog alley to digital autobahn

Today, both of those predictions have largely come true, due to Internet phenomena such as YouTube, blogging, online social networking, reality TV and webcams. If you want to see a recent example of an Internet phenomenon, try searching for `Bus Uncle' on Google or visit http://en.wikipedia.org/wiki/The_Bus_Uncle . But none of this would have been possible without ever-increasing computer speeds and the increased bandwidth necessary to exchange so much information. Let me explain.

The Analog Age ages

A football looks like, well, a football; and that's whether it is the real thing, a photograph or an oil painting of it. And there used to be a limit to how small you could make it before it would no longer be recognizable as a football. At least that was how it was when the world's technology was still `analog', which just means that the information which represented the football was very football-like.

Another example of an analog representation are the wiggly grooves in an old LP (long playing) record's surface where the wiggles actually represent the sound waves it reproduces when the record is played. These records, although they had a diameter of about 30 cm, could only store about 20 minutes of analog audio on each side. The sound quality would decrease a little each time the record was played.

Commercial, medical, historical and governmental records were all kept in analog form _ on paper. Sometimes these were converted to plastic film, called `microfiche', but this was still just very small writing.

Digital's debut

An analog signal has a continuous range of values, but a digital signal is either zero or one. An audio CD can contain information such as artist, track name, time and number as well as the music since the extra information is only a few additional zeros and ones.

So what really happened on the formatting road from analog to digital media? Simply stated, things got smaller; more specifically, information got smaller. Almost all the information you receive today is represented by the digit ``1'' or the digit ``0''. This is what we mean by digital information.

Let me give you an example. When you use your digital mobile phone your voice no longer travels as a wiggly analog signal, but is converted to digital zeros and ones that travel via microwaves through the air. Next, the pulses of laser light travel down an optical fiber. After that, your voice travels as microwaves again until your voice is received by another digital mobile phone that re-converts the ones and zeroes back into an audio signal that sounds very similar to your voice.

Digital data is independent of its interpretation. Thus, digital data of any kind _ music, movies, photographs, art, text, maps, bank accounts, or voice mail _ are all represented by zeros and ones.

Back to bandwidth

Once everything is reduced to zeros and ones it can travel along the same path. The amount of information that can be sent down a particular path depends only on the path's bandwidth, similar to the automobile traffic on a narrow street compared to a superhighway. The more information, the more bandwidth is needed. Bandwidth is measured in hertz (Hz).

The key point is that digital information requires less bandwidth than analog information, which is why we can have telephone, hundreds of TV channels and several computers connected to the Internet, using a single connection simultaneously. Another way of mentally capturing the concept is to imagine how much bookshelf space a 30-volume set of encyclopedias uses, then realize that the entire set can today be saved to a thumb drive. That's how significant the difference is between analog and digital in terms of size and portability.

A copper telephone wire has a bandwidth of millions of hertz. In the old days when it was only used to transmit analog speech patterns, this took up only about 3400 Hz, so most of the bandwidth into our homes wasn't being used. It was like having a big highway with only just a few cars using it.

Anyone who has broadband today has more than enough bandwidth, for now. The reason why it can still be slow is not because your own connection is insufficient, but because you are sharing the bandwidth of the whole Internet with every other user. There are over 400 million people in Asia alone. With thousands more new users every day, keeping the Internet functioning is a real challenge. To see how the Internet is functioning right now in Asia, or any other part of the world, go to the Internet traffic report at www.internettrafficreport.com .

Next time: Where would we be without friction?

Corrin Funnell is a laser physicist with a specialty in laser spectroscopy. He has taught in the UK, Egypt, at Thailand's own Harrow International School, where he became head of the physics department. Currently, he is head of Physics at Island School, Hong Kong.