Samsung shares were up sharply this Monday after it released details of its new range of Galaxy smartphones.  It will be a relief for investors who are hoping the new models will revive Samsung's fortunes after it announced a big drop in profit last year. 
Samsung's dominance in the smartphone world has been challenged not just by the likes of Apple but by HTC and Chinese manufacturers. Tech expert Stuart Miles is at the Mobile World Congress in Barcelona. He says Samsung has invigorated and innovated as much as it can.