Sprint confirms most of its LTE devices will be able to access 4x2 MIMO technology

Sprint (NYSE: S) has been seeding the market with devices that can support the 4x2 MIMO antenna technology the carrier disclosed it will start deploying, a company spokeswoman confirmed. The new technology is expected to improve Sprint's LTE network performance, especially at the cell edge.

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John Saw, Sprint's chief network officer, noted the deployment in a blog post about the improvements Sprint has been making to its network. Sprint is trying to catch up to its rivals in terms of LTE network breadth and speed.

"This summer we're excited to begin the installation of 8T8R radios within our 2.5 GHz footprint allowing our cell sites to send multiple data streams and achieve better signal strength," Saw wrote. "Our deployment of 4x2 MIMO at 2.5 GHz is also expected to increase data throughput and coverage without requiring additional bandwidth."

Sprint spokeswoman Kelly Schlageter confirmed to FierceWireleess that the carrier is deploying 4x2 MIMO. "It will be hardware dependent and not every device will be able to take advantage of 4x2 MIMO, but knowing it was coming, we have been pre-seeding the base for a long time and most LTE devices will be able to" take advantage of the technology, she said. "4x2 MIMO is another tool in the arsenal to provide coverage and capacity improvements to our customers."

Sprint is not the first U.S. carrier to take advantage of 4x2 MIMO technology. In April T-Mobile US (NYSE:TMUS) confirmed it had started to deploy the technology in its LTE network to enhance network performance at the cell edge and generally boost the customer experience. While T-Mobile did not say where it would do so first, GigaOM spotted 4x2 MIMO deployments in Chicago, Dallas and San Antonio, Texas.

By moving to 4x2 MIMO, both Sprint and T-Mobile are effectively doubling the number of antennas--and thus, data transmission paths--used in standard LTE deployments, which use 2x2 MIMO. MIMO sends data over two parallel transmission paths from cell towers to devices at the edge of the network.

The net effect of using 4x2 MIMO will be that customers at the cell edge will have a better chance to get a strong LTE signal since there will be more signals sent to their devices. Additionally, more antennas on towers mean that customers will also see a boost in their uplink transmissions.

In his post, Sprint's Saw promised work beyond 4x2 MIMO. "Even more exciting though is the potential for higher levels of MIMO such as 8x8 which is only possible with the use of 8T8R equipment," he wrote. "While we don't have plans today for 8x8 MIMO, this is a significant competitive advantage that we could potentially utilize at some point in the future."

Sprint expects to begin deploying 8T8R (which stands for eight transmitters and eight receivers) radio heads this summer, and in June it showed off live 8T8R radio traffic in Chicago. The new radios are a key component of Sprint Spark, the carrier's tri-band LTE service, which uses spectrum in the 800 MHz, 1900 MHz and 2.5 GHz bands. The real star of Spark though is Sprint's 2.5 GHz spectrum, which the carrier aims to have covering 100 million POPs by the end of the year. Saw said that by year-end, Sprint expects to begin 2x20 (or 40 MHz) carrier aggregation using its 2.5GHz spectrum, giving Sprint additional capacity and faster data speeds. Saw said in March that the 40 MHz carrier aggregation will enable peak downlink speeds of 120 Mbps, but that Spark users may need to purchase new devices to be able to access those faster speeds.

In the blog post, Saw said Sprint is now moving from a pure network deployment phase to network optimization. "We're focused on three areas for network optimization--coverage, interference, and capacity--to achieve the best call quality and data speeds we can deliver," he wrote. "We address all of these areas by making sure each cell site has the correct set of network parameters. Every base station has hundreds of configuration parameters that affect a customer's voice and data experience, and each of these can be altered to change the behavior of the network. The key thing here is to manage the network locally by having engineers on the ground looking at performance and tending to every site."

For more:
- see this Sprint blog post

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