Basics of LTE Technology

This tutorial section 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 

LTE tutorial-Page2

This tutorial on LTE covers following topics.


LTE is the next generation of technology which is backward compatible with cellular technologies such as HSPA,GSM,CDMA etc. LTE means Long Term Evolution.LTE which is known as 4G technology is being specified in Release 8 and 9 of the 3GPP standard. Release 10 is referred as LTE-Advanced. The LTE radio transmission and reception specifications are documented in TS 36.101 for the UE ( User Equipment) and TS 36.104 for the eNB (Evolved Node B). Downlink and uplink transmission in LTE are based on the use of multiple access technologies: specifically, orthogonal frequency division multiple access (OFDMA) for the downlink, and single-carrier frequency division multiple access (SC-FDMA) for the uplink. The work on the specifications is ongoing, and many of the technical documents are updated quarterly. The latest versions of the 36-series documents can be found at LTE Physical layer is described in TS36.211 and TS36.212 releases. 36.211 mentions physical channels and modulation while 36.212 mentions multiplexing and channel coding.

LTE system basic parameters and LTE Frame structure:

Frame Size=10ms
No. of slots=20.
No of Slots per Sub frame =2.
Slot duration=0.5 ms
Sub frame duration=1 ms
Basic time unit Ts for BW of 20MHz, (1/15000)*2048 seconds equal to 32.55ns.

There are two types of frames in LTE;FDD and TDD. Type 1, applicable to FDD- Here there are total 20 slots, each is 0.5ms. 2 slots constitute 1 sub frame. Total Frame duration is 10ms.

Type 2, applicable to TDD- Here there are 10 sub frames, each is 1 ms,sub frame 0 and 5 are dedicated for downlink always while sub frames 1 and 6 are dedicated for control frame.Sub frames 2, 3, 4 and 7, 8, 9 depend on UL/DL configuration table defined in the standard.Frame has switch point periodicity of 5 ms.

LTE Features

The key features of LTE physical layer are mentioned below.
Channel Bandwidth: 1.4/3/5/10/15/20 MHz
FFT size : 128/256/512/1024/1536/2048
Cyclic Prefix : Normal, Extended
DL multiple access: OFDMA
UL multiple access: SC-FDMA
Duplexing :FDD & TDD
Subcarrier mapping: Localized
Subcarrier hopping: Yes
Data Modulation : QPSK/16QAM/64QAM
Subcarrier spacing: 15KHz
Channel Coding : convolutional coding and turbo coding
MIMO :2 or 4 at transmit and 2 or 4 at receive side
HARQ :incremental redundancy

3GPP released documents of LTE and LTE-advanced are available at 3GPP web site-


1. TS 36.201- Evolved Universal Terrestrial Radio Access (E-UTRA); LTE physical layer; General description
2. TS 36.211- Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation
3. TS 36.212- Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding
4. LTE Terminology

LTE Tutorial related links

What is LTE?  Terminology  3GPP ref   LTE tutorial  LTE Features  UE categories  LTE Bands  EARFCN vs frequency   LTE frame  FDD vs TDD   PHY  protocol stack  throughput  VoLTE  CA
UE cell search  UE network entry  Timers  PSS vs SSS  LTE RS DMRS SRS  LTE Channels  BW vs FS vs RB  Zadoff chu sequence  LTE Advanced   eNodeB Measurements  UE Measurements  SC-FDMA Vs OFDMA   LTE Security  

RF and Wireless Terminologies