Mukesh Ambani-promoted Reliance Jio Infocomm Ltd has seen a 49% increase in its data speed after its free services ended on 31 March, according to London-based research firm Open Signal.

In the six months between reports, Jio’s average 4G download speed result climbed from 3.9 Mbps to 5.8 Mbps, the firm said.

“A likely explanation is that Jio customers began restricting their data usage once they found themselves paying for the gigabytes they consumed, though network upgrades or customer losses could also explain the shift in speeds," it said in a report released on Thursday.

Data speeds have gained much attention after the entry of Jio, which is seeking to ride on growing demand for data in India. Jio believes data will change the course of mobile telephony in India. It has disrupted the Indian telecom market first by its free services followed by ultra-cheap offers, which have eroded margins of rival telcos and impacted their bottomline.

Open Signal said that it noticed a significant drop in speed of Jio’s rivals such as Bharti Airtel Ltd, Idea Cellular Ltd and Vodafone India Ltd in the last six months.

“We measured the biggest decline in 4G speed on Airtel, falling from 11.5 Mbps to 9.1 Mbps. Meanwhile, Idea and Vodafone’s average 4G speed test fell by about a megabit each in our most recent test period," the firm said, adding that cheap data plans of these telcos have increased usage on their networks and that, in turn, may have caused more congestion on their networks and forcing average speeds to slow down.

Yet, Airtel continued to lead the speed ranking for both 3G and 4G network with average downloads of 9.1 Mbps and 3.6 Mbps respectively. Idea and Vodafone were tied at 2nd place in 4G download, each with a measured average LTE speed of 7.4 Mbps. And despite its big speed surge, Jio still ranked last in 4G speed.

“But the once yawning gulf between the fastest and slowest 4G operators has contracted, and the dynamics of speed in India are clearly changing," the firm said in its report.

The report that analysed over 7 billion measurements collected from 708,504 mobile devices from subscribers across India showed that the tested 4G speeds for Airtel, Idea and Vodafone showed that “Jio testers were able to latch onto an LTE signal more than 95.6% of the time, putting Jio 32 percentage points ahead of its nearest competitor" in the availability metric.