Ericsson, the world's biggest mobile network gear maker, said on Wednesday multimedia chief Jan Wareby would take over as the Swedish company's head of sales and marketing.

Wareby, head of Ericsson's struggling multimedia unit, was previously head of sales and marketing at Sony Ericsson, where he played an integral role in establishing the joint venture.

Ericsson said this week its chairman, Michael Treschow, would step down next year or in 2012 after helping steer the company through the market downturn and a phase of industry consolidation.

(Editing by Dan Lalor)