Tuesday, January 22, 2013

Video: The Cloud, Explained By Kids :)

Good stuff from the folks at Rackspace....... kids describing the cloud. Turn up your speakers and enjoy!

Saturday, January 19, 2013

Goodbye SMS-Based Text Messaging

ASYMCO put up an interesting piece titled What's up with text messaging? yesterday about texting in Spain. Volume is dropping rapidly with Internet Protocol (IP) based message apps like Whatsapp, Apple's iMessage and Facebook messaging replacing a voice network based text protocol called Short Message Service (SMS). SMS has been around since 1982 and has become a real cash cow for wireless providers. 

Here's more from that ASYMCO post:
  • Whatsapp reported that it set a record of 18 billion messages processed over New Year’s Eve. 
  • In October Apple announced that iMessage had delivered 300 billion messages during the preceding 12 months.
  • Globally SMS traffic is still rising. It’s expected to reach 9.6 trillion in 2012, but at least one analyst forecasts  that SMS’s share of global mobile messaging traffic will fall from 64% in 2011, to 42% in 2016.
I'd also put Skype on the list as a disruptor.

Expect similar results in the United States and other countries. Wireless providers have seen this coming for a while now and (I believe) it's the reason we've seen most implement data caps while, at the same time, encouraging customers to consume more data (translation - go over your data cap) using services like mobile video streaming. 

If you want to know more about SMS and IP based texting I've got an earlier posted titled Why Are My iPhone Text Messages Sometimes Blue and Sometimes Green? linked here.

Thursday, January 10, 2013

Tektronix Oscilloscope Tutorials

I came into Electrical Engineering a different way than most - starting as a graduate student with an undergraduate degree in Microbiology. These two disciplines are slightly different - Microbiologists use microscopes and EE's use oscilloscopes :) I knew I had some catching up to do and remember one of my major goals for the summer before I started grad school was to learn how to use an oscilloscope. Fortunately I came across a free tutorial booklet from Tektronix on understanding and using an oscilloscope which made it pretty easy.

Well, even though that was over 30 years ago now, the Tektronix free tutorial materials still exist and they are even better than before. If you are starting from scratch or just want to brush up these are highly recommended. Here's a link to the tutorial page. Good stuff!

Wednesday, January 9, 2013

Crosstalk and Copper Wires

Electrical current flowing through any conductor (like the copper wires connecting his phone) will produce a surrounding electromagnetic field. If another conductor is within the surrounding field, an inductively coupled current will flow through the adjacent conductor.

Inductively Coupled Electromagnetic Flux

In the figure above current flowing through the conducting wire will produce an inductively coupled current in the adjacent wire. If the varying signal current represents a voice transmission the conversation can crossover from one line to another and voices can be heard on one line from another line conversation. Usually this is only an annoyance since crosstalk signal levels are typically low when compared with the signal levels of the conversation on the primary line. On the other hand digital data transmissions are extremely sensitive to crosstalk. Crosstalk can cause bit misinterpretation and will typically require a retransmission of the damaged data.

There are two types of crosstalk, near end and far end.

Near End Crosstalk (NEXT)
Near end crosstalk occurs between a transmitted signal and a received signal. Transmitted signals are typically stronger that a signal that is being received and interfere with the received signals.

Near End Crosstalk

Far End Crosstalk (FEXT)
Far end crosstalk occurs between two signals transmitted in the same direction. The adjacent conductors each produce a magnetic field and can interfer with each other.

Far End Crosstalk

The most common way to reduce crosstalk between adjacent wires is to twist the wires together in a way that cancels the crosstalk flux. That's why Unshielded Twisted Pair (UTP) cabling is used for high speed data cabling like Ethernet. In addition shielding, in the form of foil or metallic braid is also used in Shielded Twisted Pair (STP) cable.