(Telecompaper) Goolge's planned mobile service will launch by the end of March, initially on the company's latest Nexus brand smartphone, people familiar with the matter told the Wall Street Journal. The service will be designed to switch between Wi-Fi and cellular networks. The new Nexus 6 smartphone will be designed by Google and made by Motorola Mobility, now part of Lenovo, two people told the paper. The service won't work with older Nexus devices, such as LG's Nexus 5. People familiar with Google's plans said it expects to launch the service in coming weeks, but the start may be delayed. It will run over the T-Mobile and Sprint networks in the US, as well as offer seamless handover for data as well as voice to Wi-Fi networks.