lte technology
DESCRIPTION
LTETRANSCRIPT
LTE Technology ; An Evolution
By;Usman Qureshi
RF Optimization EngineerChina Mobile Pakistan.
Outline• Motivation of LTE• LTE Technology Basics
Key ParametersOFDMA and Downlink Frame StructureSC-FDMA and Uplink Frame StructureNetwork & Protocol ArchitectureLTE UE categories
• Radio ProceduresCell SearchSystem Information BroadcastEPS Bearer SetupDownlink & Uplink Data TransmissionMobilityMIMO
LTE Market Situation – Based on HSPA Success Story
•HSPA growth is based on the Uptake Of Mobile Data services world wide.More than 250 networks world wide have already commercially launched HSPA.
•Mobile Data Traffic is growing Exponentially, caused by Mobileinternet offerings and improved user experience with new device types.
•LTE is accepted worldwide as the long term evolution perspective for today’s Today’s 2G and 3G networks based on WCDMA/HSPA, GSM/EDGE, TD-SCDMA, etc
Evolution of LTE (FDD & TDD)
LTE Vs HSPA
LTE – Basic Drivers
• Reduced Latency Radio Access Network Latency (User Plane UE-RNC-UE) below 10ms.
Significantly reduced control panel Latency.
• Higher User Data Rates 100 Mbps (Downlink) & 50 Mbps (Uplink)
• Improved System Capacity & Coverage Support for Scalable Bandwidth:1.4, 3 , 5, 10, 15, 20 Mhz
Support for Internetworking with Legacy networks
• Cost Reduction Reduced CAPEX & OPEX including Backhaul.
Cost Affective Migration from Legacy networks.
• Improved Spectrum Efficiency 2-4 times better than 3GPP Release 6
Support for Paired & unpaired spectrum (FDD & TDD mode)
LTE/SAE Network Architecture
Protocol Stack – User Plane
Protocol Stack – Control Plane
LTE Key Parameters
What is OFDM ?
OFDM Signal Generation Chain
OFDM Signal generation is based on Inverse Fourier Transform (IFFT) operation On transmitter side.
On Receiver side, an FFT operation will be used.
OFDMA & OFDMOFDM allocates users in time domain only
OFDMA allocates users in time & Frequency domain
LTE Downlink Frame Structure
•LTE Provides QPSK, 16QAM, 64QAM as downlink modulation schemes.•Cyclic prefix is used as guard interval, with different configurations;
Normal Cyclic Prefix Extended Cyclic Prefix
•15 Khz subcarrier spacing•Scalable Bandwidth.
OFDMA Time- Frequency Multiplexing
LTE Spectrum FlexibilityLTE Physical layer supports any bandwidth from 1.4 MHz to 20 MHz in steps of 180 KHz (resource block)Current LTE specification supports a subset of 6 different system bandwidthsAll UEs must support the maximum bandwidth of 20 MHz.
Mapping between Logical & Transport
LTE Radio Procedures
Lte Initial Access Procedure is shown below, before going into the details ofThese procudres
Downlink Physical Channels & Signals
Cell Search in LTE
Cell Search in LTE, Reference Signals
Random Access Procedure
Hybrid ARQ in the downlink
Uplink Physical Channels & Signals