Multi-mode Chipsets Enable World's First Dual-Mode HD VoLTE Call

A few years ago, Time-Division Long-Term Evolution networks (TD-LTE) received very little attention. Circumstances have changed since the Chinese are planning to deploy TD-LTE nationally as soon as the government allots the appropriate spectrum.

To capitalize on the opportunity, Ericsson, in conjunction with China Mobile, conducted the world’s first dual-mode HD VoLTE call. The call connected a TD-LTE network with a typical LTE-FDD (frequency-division duplexing) network.

TD-LTE utilizes a single block of radio frequencies to transmit calls and data over LTE networks. LTE-FDD utilizes paired radio frequency blocks, one for downstream and one for upstream. Both types of networks have their advantages.

Phil Marshall, a research analyst for Tolaga, told Computerworld that TD-LTE advocates argue that the technology is simply a more efficient and effective way to use limited amounts of spectrum.

For example, TD-LTE service more closely resembles home broadband, with thin “pipes” for functions like sending e-mail and URLs and thicker pipes for downloading the pages attached to URLs.

The asymmetric provisioning of TD-LTE, Marshall explains, utilizes networks to their full capacity instead of leaving a lot of unused capacity on the uplink side.

LTE-FDD, on the other hand, harks from a time when voice traffic made upstream and downstream signaling relatively balanced. “The advocates of FDD will tell you that you get better performance consistency with FDD and it is easier to implement,” said Marshall, “particularly when coordinated with other FDD systems.”

According to Ericsson, TD-LTE and LTE-FDD share a technical similarity of over 90 percent. Ericsson’s Thor LTE modem along with quad-mode chipsets from Renesas Mobile can share a common commercial platform and are on deck for mass production.

Ericsson also pointed out that TD-LTE technology allows operators to free up their 2G and 3G frequency bands in an era where spectrum is becoming increasingly scarce.

“Ericsson is honored to support China Mobile in establishing yet another milestone in the development of TD-LTE,” said Mats Olsson, president of Ericsson North East Asia.

“The technology readiness and commercial availability of the system, platform and devices for TD-LTE that we demonstrated here is a strong testimonial to the maturity of a converged end-to-end TD-LTE ecosystem.”