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An Introduction of
3GPP Long Term Evolution (LTE)
Speaker：Tsung-Yin Lee
Reference
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http://www.tcs.com “LTE-Advanced: Future of Mobile Broadband,”
TATA Consultancy Services
Takehiro Nakamura ,“Proposal for Candidate Radio Interface Technolo
gies for IMT‐Advanced Bas d on LTE Release 10 and Beyond,”
3GPP TSG‐RAN Chairman
“3GPP LTE Channels and MAC Layer,” EventHelix.com Inc. 2009
Ahmed Hamza, Network Systems Laboratory Simon Fraser University,
“Long Term Evolution (LTE) - A Tutorial,” October 13, 2009
Jim Zyren, “Overview of the 3GPP Long Term Evolution Physical
Layer,” Document Number: 3GPP EVOLUTIONWP Rev0 07/2007
David Astély, Erik Dahlman, Anders Furuskär, Ylva Jading, Magnus
Lindström, and Stefan Parkvall, Ericsson Research, “LTE: The
Evolution of Mobile Broadband” , IEEE Communications Magazine,
April 2009
2
Outline
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History of 3GPP LTE
Basic Concepts of LTE
Introduction of LTE Protocol
Compare with LTE and LTE-Advanced
Conclusion
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What is LTE ?
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In Nov. 2004, 3GPP began a project to
define the long-term evolution (LTE) of
Universal Mobile Telecommunications
System (UMTS) cellular technology
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Higher performance
Backwards compatible
Wide application
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Evolution of Radio Access
Technologies
802.16m
802.16d/e
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LTE (3.9G) :
3GPP release 8~9
LTE-Advanced :
3GPP release 10+
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LTE Basic Concepts
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LTE employs Orthogonal Frequency
Division Multiple Access (OFDMA) for
downlink data transmission and Single
Carrier FDMA (SC-FDMA) for uplink
transmission
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Multipath-Induced Time Delays Result
in Inter-Symbol Interference (ISI)
y (t )  S (t )  S (t  m)  n(t )
βS(t-m)
S(t)
y(t) : output signal
S(t) : input signal
S(t-m) : delayed m time input signal
n(t) : noise
y(t)
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Equalizers in Receiver
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Against Frequency Selective Fading
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Channel transform function Hc(f)
y (t )  S (t )  S (t  m)
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H c ( f )  1   e  j 2fm
Equalizers transform function Heq(f) (Receiver)
1
1
Hc ( f ) 

H c ( f ) 1  e  j 2fm
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Frequency Selective Fading
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the coherence bandwidth of the channel is
smaller than the bandwidth of the signal
Frequency Correlation > 0.9
Bc = 1 / 50α α is r.m.s. delay spread
It may be useless for increasing transmission power
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Cyclic Prefixes
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FDM vs. OFDM
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LTE-Downlink (OFDM)
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Improved spectral
efficiency
Reduce ISI effect
by multipath
Against frequency
selective fading
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LTE Uplink (SC-FDMA)
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SC-FDMA is a new single carrier multiple access
technique which has similar structure and
performance to OFDMA
A salient
advantage of SCFDMA over
OFDM is low to
Peak to Average
Power Ratio
(PAPR) :
Increasing
battery life 13
Multi-antenna techniques
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Generic Frame Structure
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Allocation of physical resource blocks
(PRBs) is handled by a scheduling function
at the 3GPP base station (eNodeB)
Frame 0 and frame 5 (always downlink)
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Resource Grid
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One frame is 10ms
 10 subframes
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One subframe is 1ms
 2 slots
One slot is 0.5ms
 N resource blocks
[ 6 < N < 110]
One resource block is 0.5ms
and contains 12 subcarriers
from each OFDM symbol
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LTE spectrum (bandwidth and
duplex) flexibility
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LTE Downlink Channels
Paging Control Channel
Paging Channel
Physical Downlink Shared Channel
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LTE Uplink Channels
Random Access Channel
CQI report
Physical Uplink Shared Channel
Physical Radio Access Channel
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LTE Release 8 Key Features (1/2)
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High spectral efficiency
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Very low latency
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OFDM in Downlink
Single‐Carrier FDMA in Uplink
Short setup time & Short transfer delay
Short hand over latency and interruption time
Support of variable bandwidth
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1.4, 3, 5, 10, 15 and 20 MHz
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LTE Release 8 Key Features (2/2)
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Compatibility and interworking with earlier
3GPP Releases
FDD and TDD within a single radio access
technology
Efficient Multicast/Broadcast
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Evolution of LTE-Advanced
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Asymmetric transmission bandwidth
Layered OFDMA
Advanced Multi-cell
Transmission/Reception Techniques
Enhanced Multi-antenna Transmission
Techniques
Support of Larger Bandwidth in LTEAdvanced
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Asymmetric transmission
bandwidth
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Symmetric transmission
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voice transmission : UE to UE
Asymmetric transmission
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streaming video : the server to the UE (the downlink)
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Layered OFDMA
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The bandwidth of basic frequency block is,
15–20 MHz
Layered OFDMA radio access scheme in
LTE-A will have layered transmission
bandwidth, support of layered environments
and control signal formats
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Advanced Multi-cell
Transmission/Reception Techniques
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In LTE-A, the advanced multi-cell
transmission/reception processes helps in
increasing frequency efficiency and cell
edge user throughput
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Estimation unit
Calculation unit
Determination unit
Feedback unit
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Enhanced Multi-antenna
Transmission Techniques
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In LTE-A, the MIMO scheme has to be further improved
in the area of spectrum efficiency, average cell through put
and cell edge performances
In LTE-A the antenna configurations of 8x8 in DL and 4x4
in UL are planned
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Enhanced Techniques to Extend
Coverage Area
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Remote Radio Requirements (RREs) using optical
fiber should be used in LTE-A as effective
technique to extend cell coverage
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Support of Larger Bandwidth in
LTE-Advanced
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Peak data rates up to 1Gbps are expected
from bandwidths of 100MHz. OFDM adds
additional sub-carrier to increase bandwidth
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LTE vs. LTE-Advanced
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Conclusion
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LTE-A helps in integrating the existing
networks, new networks, services and
terminals to suit the escalating user
demands
LTE-Advanced will be standardized in the
3GPP specification Release 10 (LTE-A) and
will be designed to meet the 4G
requirements as defined by ITU
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Backup
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LTE Downlink Logical Channels
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LTE Downlink Logical Channels
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LTE Downlink Transport Channel
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LTE Downlink Transport Channel
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LTE Downlink Physical Channels
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LTE Downlink Physical Channels
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LTE Uplink Logical Channels
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LTE Uplink Transport Channel
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LTE Uplink Physical Channels
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