A smartphone generates much less mobile data traffic than a laptop with a data card, but phones impose a load on the network which is much larger than anticipated, a study showed on Wednesday.

A boom in mobile data traffic -- boosted by laptops and smartphones -- is putting unprecedented stress on wireless networks around the world.

Delivering the same amount of data, a smartphone typically generates eight times the network signaling load of a laptop with a data card, a study by technology firm Airvana Inc showed.

They are always on ... in a chatty way, said David Nowicki, vice president of marketing and product management at Airvana.

Global annual shipments of smartphone handsets are projected to increase from nearly 200 million in 2009 to 450 million in 2013, according to market research firm iSuppli.