In the quest to meet ever-growing mobile data demands, Long Term Evolution (LTE) time-division duplexing (TDD) has taken the lead as a potential global 4G standard. The shift from expanding coverage to providing higher data speeds and increased capacity has been the main driver of LTE TDD’s success, according to the latest report from Strategy Analytics. The exploration of new spectrum bands to support traffic—specifically, the 3.5-GHz band—also is a key component.
LTE TDD’s efficiency is supported by its ability to leverage common LTE networking equipment with higher frequency bands. For example, Sprint’s Spark program increases broadband capacity by utilizing the higher bands. At the same time, it re-frames the lower frequencies to provide good coverage and spectral efficiency (see “Combined Wireless-Network Approach Runs at 50 To 60 Mb/s” on Microwaves & RF). The lower frequency bands provide nationwide coverage, whereas the higher frequency bands offer higher-data-speed throughput.
Sprint’s parent company, Softbank, has deployed over 43,000 2.5-GHz LTE TDD base stations since 2011. They complement its LTE full-division-duplexing (FDD) network at the 900-MHz and 2.1-GHz bands. In addition, the company has been keeping a close eye on the 3.5-GHz band—especially with Japanese regulators planning to reallocate the band for mobile broadband service in 2015. In September 2013, Softbank and Huawei completed a trial to test the offload solution for LTE TDD small cells in the 3.5-GHz band. The system was able to leverage five component carriers for an aggregated data rate to 770 Mbps. The advanced carrier aggregation (CA) used by the system proved to be a viable solution for efficient offloading of macro-networks.
Performing as the duplexing mode of the 3GPP LTE standard, Strategy Analytics points out that LTE TDD shares the same network architecture, protocol stack, and physical-layer technologies with former systems. In addition to seamless interworking, this approach ensures that operators with limited access and resources can reduce operating costs and provide enhanced experiences.
Strategy Analytics also notes that various operators are continuing to improve LTE data speeds by deploying additional carriers in new frequency bands. In addition, they are planning for advanced features like LTE-Advanced Release 10 carrier aggregation and small-cell HetNets. In another example of an integrated solution, Nokia Solutions and Networks (NSN) has demonstrated TDD-FDD carrier aggregation with Korea Telecom (KT) and SK Telecom (SKT).