Of FDD & TDD LTE
The dust has barely settled on the battle between Wimax and LTE, the competing wireless broadband technologies. Fourth-generation or 4G technology LTE won much to the disappointment of technology giant Intel that had put its might and money behind Wimax. But now, a new battle is beginning between two flavours of LTE: TDD LTE and FDD LTE.
Many large corporations are stakeholders in this battle. How this battle will play out depends a lot on cellular operators, network equipment manufacturers and mobile handset makers. For now it is a Catch 22 situation. Manufacturers will back the system that has, or will have, the most user base because it means a big market for them. Cellular Operators will choose the technology that has the backing of the manufacturers because that means competition among manufacturers bringing down prices. Long Term Evolution or LTE is a wireless communication standard that builds on existing GSM technology. It allows for faster data transmission and improved download capacities. For effective communication, radio signals should travel in both directions carrying voice or data as the case may be. That calls for what is technically referred to as a duplex scheme, which organises transmission and reception simultaneously in such a way that there is no interference between the two. This can be done by separating transmission and reception using either time or frequency
WHAT’S FDD? Within a specified frequency band, two frequency channels are created separated by sufficient frequency distance and the two are used as dedicated channels for sending and receiving signals simultaneously. This is called frequency division duplex or FDD. Typically for FDD, paired spectrum is required and has to be auctioned as such by the regulatory authorities
WHAT’S TDD? If frequency is a scarce commodity, as it is in India, then the cellular operators may not have the luxury of a large frequency band available that can then be carved out into dedicated sending and receiving channels. In that case, then time is used as the separator between sending and reception of signal. Short bursts of transmission and reception are done separated in fractions of a second. This is called Time Division Duplex or TDD, which is better suited for data than voice. In data, there is usually more of reception or download than upload and the system can be tweaked to allow for greater download time and shorter upload time.