Bandwidth planning has become a tricky business since data traffic completely displaced voice as the driver of consumption. Not only is demand more variable and uncertain, growth is more dynamic, by an order of magnitude or two.
That raises an obvious question for mobile service providers: how much bandwidth do they need to be ready to supply to customers? The question might be easier to answer if demand were not if end user demand was predictable, but demand is not predictable. Sometimes growth is “only” 40 percent a year; sometimes it is higher.
Cisco in early 2011, for example, estimated that global mobile data traffic grew 2.6-fold in 2010–just one year–nearly tripling for the third year in a row.
In fact, the 2010 mobile data traffic growth rate was higher than anticipated, according to Cisco. In 2009 the growth rate would be 149 percent. In 2010 global mobile data traffic grew 159 percent.
And it is video traffic that is the real story. Mobile video traffic was expected to exceed 50 percent for the first time in 2011. Mobile video traffic was 49.8 percent of total mobile data traffic at the end of 2010, and will account for 52.8 percent of traffic by the end of 2011, Cisco has maintained.
According to Cisco, mobile data traffic now matches the 1:20 ratio that has been true of fixed networks for several years, meaning that one percent of the users consume 20 percent of all the bandwidth.
Similarly, the top 10 percent of mobile data subscribers now generate approximately 60 percent of mobile data traffic.
Average smart phone usage doubled in 2010. The average amount of traffic per smartphone in 2010 was 79 MB per month, up from 35 MB per month in 2009. Almost nobody would be surprised if usage doubled again in 2011.
Smart phones represent only 13 percent of total global handsets in use today, but they represent over 78 percent of total global handset traffic. In 2010, the typical smart phone generated 24 times more mobile data traffic (79 MB per month) than the typical basic-feature cell phone (which generated only 3.3 MB per month of mobile data traffic).
Globally, 31 percent of smart phone traffic was offloaded onto the fixed network through dual-mode or femtocell in 2010. In 2010, 14.3 petabytes of smartphone and tablet traffic were offloaded onto the fixed network each month.
Without offload, traffic originating from smart phones and tablets would have been 51 petabytes per month rather than 37 petabytes per month in 2010.
But bandwidth growth is very hard to predict. Some might say, for example, that over the past year, AT&T has revised its own forecasts of bandwidth consumption in significant ways.
In a March 2011 presentation AT&T projected that data volumes would grow by eight to 10 times between the end of 2010 and the end of 2015.
That forecast appears to be based on an expectation that volumes would roughly double in 2011 and then increase by a further 65 percent in 2012.
Instead, AT&T now seems to be seeing 40 percent annual growth. Now, 40 percent annual growth is significant. It means bandwidth consumption doubles about every two to three years.
But annual bandwidth growth of 50 percent a year would be well within historical ranges, on an aggregate basis, in terms of long-haul bandwidth consumption. But policies and end user behavior can change the demand curve.
The most-recent AT&T forecast would mean that data volumes would increase by five to six times by 2015. Whether that means existing spectrum, and newer methods for handling traffic using that spectrum, are sufficient to handle future growth is debatable. Some might argue additional spectrum is not required.
Others might say the possible growth of between 500 percent and 1,000 percent, in just four years, is challenging enough that additional spectrum is likely to be needed, especially if the higher range of growth turns out to be the case.