Reliance Jio opened up its 4G-only network to customers last year HIGHLIGHTS OpenSignal says Jio has the largest 4G network, but slowest speedsAirtel offers the best 4G speeds, followed by Vodafone, and IdeaOpenSignal is a popular wireless coverage mapping company Networks speeds and coverage are in focus once again as wireless coverage mapping company OpenSignal has released the latest edition of its report on the state of mobile networks in India. According to the report, Reliance Jio lags behind Airtel, Vodafone , and Idea in terms of 4G speeds, but is market leading in terms of 4G coverage. Like Speedtest before it , OpenSignal says Airtel offers the fastest 4G speeds, and Vodafone takes the second spot, closely followed by Idea at third place, while the Mukesh Ambani-owned telco rounds up the list at the fourth spot. However, in terms of overall download speeds (which includes 3G and 4G), Jio is ahead of the pack, with Airtel, ...