The Los Angels Times wrote a good article covering this exact subject. The quick answer is that text messages are 160 characters because that is the amount of space they could erk out of the control channel for cell phones. Of course this also explains the reason why the character set for text messages is also more limited. The one thing I think most people miss though is how much profit they give the cell phone companies with text messages. Since texts are sent over the control channel that means that normally this channel would normally only be used for telling the tower where a phone is and checking if it has a signal. Since this is not done very often and the bandwidth is never utalized texts work perfectly. Of course the great irony here is that the cost of these messages is pretty much nothing since these channels needed to be available at all time and there is no real disruption from using text message. In other words texting is pure profit for the cell phone companies. Just remember this next time you decide to text your friend instead of make a phone call.
Links
