3G Americas, a wireless industry trade association representing the GSM family of technologies including LTE, has published an educational white paper titled, 3GPP LTE for TDD Spectrum in the Americas (pdf). The report recommends Time Division Duplex (TDD) technology with LTE as a mobile broadband solution to utilize valuable TDD spectrum assets in the region (mostly by getting a piece of Clearwire’s 2.5-2.690 Mhz band).
In the United States, Verizon and AT&T are making plans for the deployment of LTE Frequency Division Duplex (FDD) technology, in the 700 MHz band. But that’s not a lot of spectrum. LTE in fragmented TDD spectrum, may be available in the AWS band (1.7/2.1 GHz), 2.3 GHz, 3.65GHz and the 2.5 GHz band says the report.
WiMAX currently uses TDD. Mobile WiMAX operators like Clear generally devotes a single 10MHZ channel for both upstream and downstream communications. Cellular operators generally devote two 5 MHz channels for communications, one up and one down. TDD can be more efficient for data communications since traffic can be predominantly downstream. WiMAX may also use unlicensed bands such as white spaces, 2.4 GHz and 5.8 GHz, unlike cellular-based LTE.
Fifteen paired (for FDD operation) and eight unpaired (for TDD operation) spectrum bands have been identified by the 3GPP for LTE. This means an operator can introduce LTE in new spectrum bands. The interference between LTE TDD and the other system in some cases could be handled with appropriate filtering and careful deployment and spectrum guard bands,says 3G Americas.
The cellular-based organization says the technical synergy between LTE TDD and TD-SCDMA operators will increase the economies of scale for LTE TDD operators throughout the world. LTE TDD is considered a natural evolution path of the Chinese-based TD-SCDMA system.
