Optus' average network speed also fell, from 19.44 Mbps to 14.72 Mbps, with Vodafone's at 13.9 Mbps. The OpenSignal report shows that 4G download speeds slowing is a global phenomenon. Illustration: Simon Bosch The higher the Mbps, the faster a user can browse the web or download content, with smoother streaming of video and music as well. Overall, Australia slipped from claiming the best network speeds in the world to 14th. Coverage has improved however, with the amount of time Telstra users spent connected to 4G jumping to 76.8 per cent from 64.2 per cent. Optus came in at 73.3 per cent, up from just 48.4 per cent, while Vodafone sits at 65.19 per cent.

In Australia, 4G networks are currently reserved for mobile data usage only, while voice calls are transmitted over the 3G network. Telstra was one of the first telecommunications companies in the world to launch a 4G network. 4G speeds are slowing down, a new report suggests. The exponential growth in Australians' mobile data usage in recent years has meant that once speedy 4G networks are now more congested. Telecommunications analyst Paul Budde said it was "easy" for Telstra, and Australia, to have once claimed the fastest 4G network because we were one of the first countries to launch 4G. But the OpenSignal report, sourced from 11 million people using 4G networks across the globe via a smartphone app, shows that slowing speeds are a global phenomenon.

Spain now claims the highest average 4G speeds at 18 Mbps according to the latest figures, which cover November to January, inclusive. That is more than 6 Mbps slower than Telstra's previous world-first average, recorded during the second half of 2013. Mr Budde warned that things would get worse for consumers if telcos didn't invest. "With more people [using 4G] and more broadband use it will go slower unless further investments are made," Mr Budde said. "People get used to [faster] speeds so they will notice those drops - especially the heavy users." 4G networks will experience additional traffic when telcos bring voice calls to 4G using Voice over LTE (VoLTE) technology, with Telstra expected to do so as soon as April.

Despite slowing speeds, the OpenSignal report found 4G was still on average the fastest network technology available, outperforming 3G and Wi-Fi by "a considerable margin" globally. Principal analyst at research firm Ovum, Nicole McCormick, said Australian telcos "need not be overly concerned" about the findings. "Australian telcos continue to push the technology front on improving peak data speeds, including the deployment of carrier aggregation," Ms McCormick said. Carrier aggregation lets telcos scrape extra capacity from their networks by aggregating different radio frequencies. A Telstra spokesperson said the figures from OpenSignal were "widely varying" compared to its own network test results, as well as testing of its network by other third parties.

"On this basis we do not regard this report as an accurate representation and comparison of 4G network performance and speed between countries or between carriers within a country," the spokesperson said. An Optus spokesperson said users experienced different network speeds depending on "a number of factors", including the device used, the number of users on the network, and proximity to mobile phone towers. Are you satisfied with your mobile network speed and coverage? Let us know in the comments.