6 key gadgets and trends at Mobile World Congress

The Mobile World Congress, the sector's biggest trade fair which wrapped up in Barcelona on Thursday, was dominated this year by the arrival of virtual reality, advances in the development of ultra-fast 5G networks and connected objects.

ROBOT-TELEPHONE THAT READS YOUR MESSAGES: Japanese firm Sharp presented a tiny prototype robot called RoBoHon that doubles as a mobile telephone. It has voice recognition and is able to answer questions by searching online when asked, can take pictures and read text messages you receive out loud.

HOLOGRAMS MAKE AN APPEARANCE: Which science fiction fan has not dreamed of being able to speak to someone far away by hologram? Several firms believe this will be possible when faster 5G mobile networks are running.

Among them is US start-up Leia Inc, named after the heroine of the "Star Wars" franchise, which presented a system that creates a 3D image that appears to float above the screen of a tablet.

SK Telecom's stand featured a beam of green light which caused different images to appear inside it such as a dolphin, a heart or a gymnast's movement.

INVISIBLE CHARGERS: Say good-bye to tangled wires and misplaced charging cables.

Spanish start-up MiniBatt presented a smartphone charging system that can be installed in any piece of furniture, regardless of the material. To charge a device, you just have to put it on top of a desk, chair or table. The company hopes to convince furniture makers to incorporate the charger into its designs.

SMARTPHONE MAKERS BET ON VIRTUAL REALITY: LG unveiled its new virtual reality headset, the 360 VR, which works with its new G5 smartphone.

Rival South Korean firm Samsung revealed its new flagship smartphone, the Galaxy 7, via a virtual reality presentation that used its Gear VR headsets.

Among the most visited stand was South Korea's SK Telecom, which offered a virtual reality ride under water in a yellow submarine, and another by Samsung featuring a virtual reality rollercoaster ride using its Gear VR headsets.

5G REMAINS KEY FOR SECTOR: Several equipment makers and telecom operators offered demonstrations of advantages the new network will bring such as lower latency, or reaction times.

But there were no major announcements on the development of ultra-fast 5G mobile networks, due to be rolled out in 2020 following large-scale testing in 2018.

The European Union did say it will launch an action plan to develop 5G networks and ensure Europe does not fall behind other regions as it did with the 4G network, which is in widespread use at the moment.

MORE CONNECTED OBJECTS: Connecting appliances and other objects to the Internet is the focus of more and more discussions, despite the delays in making it happen.

Research firm Gartner forecasts that the market for Internet of Things services will top $101 billion (92 billion euros) this year, nearly 30 percent more than the $78 billion that businesses spent last year.