SAN JOSE, Calif. — WiMax networks are facing a slowdown in revenue and subscriber growth this year. Meanwhile, many carriers still harbor concerns about whether the rival fourth generation wireless technology, Long Term Evolution (LTE), is ready for deployment.

Those were two conclusions from the latest quarterly report on next-generation wireless by Maravedis Research. The market watcher's 4GCounts service said in the first three months of 2009 carriers added 400,000 new subscribers to WiMax services compared to 50 million for 3G services.

"Global service revenue growth is tapering off as WiMax operators experience ARPU [average revenue per user] stagnation and subscriber growth slowdown," said Adlane Fellah, chief executive of Maravedis, speaking in a press statement.

Maravedis estimated carriers recorded ARPU in the first three months of 2009 for residential and business WiMax users of US$42.43 and US$116.82, respectively. That's flat to down from US$42.33 and US$122.64 per user for the last three months of 2009.

Clearwire USA continues to be the top WiMax operator with 500,000 subscribers at the end of March, an increase of five percent over December. As much as 54 percent of all WiMax customer equipment is vendor proprietary, Maravedis estimated, with the rest split between equipment compliant with 802.16 and .16e standards.

By contrast the top 30 carriers committed to migrating to LTE accounted had 1.1 billion cellular subscribers in March, almost half of them belonging to China Mobile, according to the report. Those carriers are using a mix of GSM, 3G and HSPA today.

Some 37 percent of carriers currently see LTE as their preferred option for fourth-generation wireless technology. However, a substantial minority of operators said they foresee delays deploying LTE, pointing to concerns about a lack of interoperability in LTE vendor products and a lack of spectrum.