Difference Between FDD LTE (FD-LTE) and TDD LTE (TD-LTE) Networks


FDD LTE and TDD LTE are two different standards of LTE 4G Technology. LTE is a high speed wireless technology from 3GPP standard. 3G growth ends up at HSPA+ and mobile operators have already started deploying 4G networks to provide much more bandwidth for mobile users. 4G speed will give us a virtual LAN reality to mobile handset by offering very high speed access to Internet to experience the real triple play services such as data, voice and video from a mobile network.

Already 4G smart phone handsets are released by Motorola, LG, Samsung and HTC,  most of them with Android operating system. Android Wi-Fi hotspot feature enable users to use the 4G mobile as replacement of home broadband services. US’s big carrier Verizon and Telia Sonera from Sweden have already started offering 4G services based on LTE technology.

LTE is defined to support both paired spectrum for Frequency Division Duplex (FDD) and unpaired spectrum for Time Division Duplex (TDD). LTE FDD uses paired spectrum that comes from a migration path of 3G network whereas TDD LTE uses unpaired spectrum that evolved from TD-SCDMA.

Difference Between FD LTE and TD LTE

(1) TD LTE does not require paired spectrum since transmit and receive occurs in the same channel whereas in FD LTE , it requires paired spectrum with different frequencies with guard band.

(2) TD LTE is cheaper than FD LTE since in TD LTE no need of diplexer to isolate transmission and receptions.

(3) In TD LTE, its possible to change the uplink and downlink capacity ratio dynamically according to the need whereas in FD LTE capacity is determined by frequency allocation by the regulatory authorities. So it is difficult to make dynamic change.

(4) In TD LTE larger guard period is necessary to maintain the uplink and downlink separation which will affect the capacity whereas in FD LTE the same concept is referred as guard band for isolation of uplink and downlink which will not affect the capacity.

(5) Cross slot interference is there in TD LTE which is not applicable to FD LTE.