Nokia is due to unveil its cheapest Windows Phone smartphone model to date at next week’s Mobile World Congress, according to Reuters sources. The company has so far unveiled three Windows-powered smartphones – the Lumia 710, 800 and 900 – but plans to target a wider market with the new device, reportedly named the Lumia 610. The sources added that a global version of the Lumia 900, currently only available in the US, will also be introduced at the event.