By William Dudley

Working here gives us a unique perspective into the SMS traffic patterns from around the world ? in fact, SMS traffic patterns from and to almost 900 wireless carriers.

When some significant event occurs somewhere in the world, regardless of it being a local, regional or global event, it can and does affect text messaging to and from that locale. Why is this? Does SMS work when a simple ?pick-up-the-phone-and-call? does not? 

The simple answer is yes, it does. 

When the immensely strong earthquake occurred in Chile on Feb. 27, SMS traffic for the carriers? networks that were not initially damaged surged to as much as ten times the normal hourly volumes for the first 24 hours or so.  

Since that time, international SMS traffic from all Chilean carriers has remained at double the levels before the earthquake. Each time there is a significant aftershock, SMS surges again for a few hours afterwards ?  as it did March 11 after that morning?s three 6.9, 6.7 and 6.0 aftershocks. 

In areas such as Chile where significant events are occurring, people find that it is easier to communicate by using SMS than making a voice call. The same was true for people trying to call areas prior to the Pacific-wide tsunami warning that was issued after the Feb. 27 earthquake.

The Haiti earthquake generated similar traffic results once the mobile networks were operational.

My wife and I actually had close friends that were vacationing in Hawaii at the time. We managed to get a voice call to them around noon, Eastern time, Saturday, but soon after that, were unable to reach them due to network overload. For the rest of the day, we communicated via SMS without issue.

Mobile networks? radio networks are divided between control channels and traffic channels.

Control channels are a small part of the radio frequency or bandwidth that are used to send information about call setups. SMS uses the control channels for delivery. 

The control channel also provides information about the traffic channels such as availability. Have you ever tried to initiate a mobile call and received a ?network busy? signal or notification? That is where there is no available room on the traffic channels for a particular tower. 

Traffic channels have significantly more bandwidth than do the control channels, but control channels are not held up as long as traffic channels.

So when multiple calls are in progress, as when there is some event, the traffic channels are allocated. However, there is almost always control channel room for SMS traffic.

Even if there is no network capacity to deliver the message immediately, SMS messages are stored by the carrier?s SMSC, so when the network capacity is available, the message is then delivered.

The reason SMS traffic continues at higher rates after the event, than before, is because people realize how easy, inexpensive and effective it is to send quick texts and these events literally cause converts.

Also, in many areas, voice capacity may remain at diminished levels, thus SMS becomes the only reliable way to communicate.

Whether the event is a once-in-a-lifetime disaster, a football game or concert, an election, a significant news event or simply a popular holiday, SMS traffic is affected. But many times, SMS becomes one of the only reliable means of mobile, consumer communications during and after.  

So remember, if you need to reach someone ? do not forget that SMS may be your only reliable channel.

William Dudley is group director of product management at Sybase 365, Reston, VA. Reach him at .