LTE frame structure | TDD and FDD frame structure of LTE

This page covers LTE Frame structure including subframe and slot structure. It describes LTE TDD frame structure and LTE FDD frame structure as per 3GPP standard.

There are two topologies used in LTE system viz. TDD and FDD. TDD stands for Time Division Duplex where as FDD stands for Frequency Division Duplex. In TDD system, same carrier frequency is used in both transmit and receive path at different time instants say 't1' and 't2'. In FDD system, different carrier frequencies such as 'Fc1' and 'Fc2' are used by transmit and receive paths at same time instant say 't1'.


LTE FDD topology

As shown in the figure, for LTE FDD mode, 'f1' and 'f2' are one pair of carrier frequencies allocated separately for both the uplink and downlink directions. The downlink refers to transmission from LTE eNodeB to UEs and uplink refers to transmission from UEs to eNodeB.

TDD LTE topology

As shown in the figure, for LTE TDD mode, same carrier frequency 'f1' is allocated in both the uplink and downlink directions. This frequency is used by both uplink and downlink at different time slots for mapping their information data. Refer FDD vs TDD LTE >> which describes LTE FDD and LTE TDD modes with examples.

LTE Frame structure

As mentioned as per topologies, TDD and FDD there are two frame structures viz. type-1 and type-2 LTE frame structure. Total Frame duration is about 10ms. There are total 10 subframes in a frame. Each subframe composed of 2 time slots.

LTE FDD frame structure

Type 1 is used as LTE FDD frame structure. As shown in the figure below, an LTE TDD frame is made of total 20 slots, each of 0.5ms. Two consecutive time slots will form one subframe. 10 such subframes form one radio frame. One subframe duration is about 1 ms. Hence LTE radio frame will have duration of about 10ms. Each radio frame will have 307200 Ts. Where in one Ts equals 1/(15000 x 2048) seconds.

LTE TDD frame structure

Type 2 is used as LTE TDD frame structure. As shown in the figure, here radio frame composed of two half frames, each of 5ms duration resulting in total frame duration of about 10ms. Each radio frame will have total 10 subframes,each subframe will have 2 time slots. subframe configuration is based on Uplink downlink configuration(0 to 6). Usually in all the cases, subframe #0 and subframe#5 is always used by downlink. The Special subframe carry DwPTS(Downlink Pilot Time Slot),GP(Guard Period) and UpPTS(Uplink Pilot Time Slot). For the 5ms DL to UL switch point periodicity case, SS(Special subframe ) exists in both the half frames. For the 10ms DL to UL switch point periodicity case, SS exists only in first half frame.

UL and DL configuration of TDD LTE frame structure

The table mentions DL and UL configuration which determines the contents of the subframes in LTE frame structure. In the table, 'U' stands for Uplink, 'D' stands for Downlink and 'S' stands for special subframe.

This LTE tutorial on LTE basics covers following sub topics:
Main page  features  terminologies  Frame  TDD FDD  Channel types  PHY  stack  throughput  VoLTE  CA   cell search  network entry  Timers  PSS vs SSS  Security   LTE Bands  EARFCN  Hotspot  router 

Frame structure of wireless standards, technologies

Frame structure of various wireless standards/technologies are mentioned below. It include WiMAX, WLAN, Zigbee, GSM, GPRS, UMTS, LTE, TD-SCDMA, GPS, SDH, 11ac WLAN, AMPS, Ethernet, VLAN etc.

WiMAX physical layer Frame Structure as per 802.16d and 802.16e standards
WiMAX MAC layer Frame Structure as per OFDM 802.16d standard
Zigbee RF4CE Frame Structure
Zigbee physical layer Frame Structure
Zigbee MAC layer Frame Structure
GPRS Frame Structure
GPS Frame Structure
LTE Frame Structure
TD-SCDMA Frame Structure
UMTS Frame Structure
SONET Frame Structure
SDH Frame Structure
802.11ac PHY Frame Structure
802.11ac MAC layer Frame Structure
WLAN Frame Structure as per 802.11a,11b,11n,11ac standards
AMPS Frame Structure
Ethernet Frame Structure
VLAN Frame Structure
GSM Frame Structure

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