An Introduction of 3GPP Long Term Evolution (LTE)
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Transcript of An Introduction of 3GPP Long Term Evolution (LTE)
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Reference http://www.tcs.com “LTE-Advanced: Future of Mobile Broadband,”
TATA Consultancy Services Takehiro Nakamura ,“Proposal for Candidate Radio Interface Technol
ogies 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
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Outline
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 ?
In Nov. 2004, 3GPP began a project to define the long-term evolution (LTE) of Universal Mobile Telecommunications System (UMTS) cellular technology Higher performance Backwards compatible Wide application
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Evolution of Radio Access Technologies
LTE (3.9G) : 3GPP release 8~9
LTE-Advanced :3GPP release 10+
802.16d/e
802.16m
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LTE Basic Concepts
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)
)()()()( tnmtStSty
y(t) : output signalS(t) : input signalS(t-m) : delayed m time input signaln(t) : noise
y(t)
βS(t-m)
S(t)
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Equalizers in Receiver
Against Frequency Selective Fading Channel transform function Hc(f)
Equalizers transform function Heq(f) (Receiver)
fmjc efH 21)(
fmjc
c efHfH 21
1
)(
1)(
)()()( mtStSty
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Frequency Selective Fading
the coherence bandwidth of the channel is smaller than the bandwidth of the signal
It may be useless for increasing transmission power
Frequency Correlation > 0.9Bc = 1 / 50α α is r.m.s. delay spread
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LTE-Downlink (OFDM)
Improved spectral efficiency
Reduce ISI effect by multipath
Against frequency selective fading
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LTE Uplink (SC-FDMA) SC-FDMA is a new single carrier multiple access
technique which has similar structure and performance to OFDMA
A salient advantage of SC-FDMA over OFDM is low to Peak to Average Power Ratio (PAPR) :
Increasing battery life
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Generic Frame Structure
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
One frame is 10ms 10 subframes
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 Uplink Channels
Random Access Channel
Physical Radio Access Channel
Physical Uplink Shared Channel
CQI report
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LTE Release 8 Key Features (1/2)
High spectral efficiency OFDM in Downlink Single‐Carrier FDMA in Uplink
Very low latency Short setup time & Short transfer delay Short hand over latency and interruption time
Support of variable bandwidth 1.4, 3, 5, 10, 15 and 20 MHz
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LTE Release 8 Key Features (2/2)
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
Asymmetric transmission bandwidth Layered OFDMA Advanced Multi-cell
Transmission/Reception Techniques Enhanced Multi-antenna Transmission
Techniques Support of Larger Bandwidth in LTE-
Advanced
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Asymmetric transmission bandwidth Symmetric transmission
voice transmission : UE to UE Asymmetric transmission
streaming video : the server to the UE (the downlink)
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Layered OFDMA
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
In LTE-A, the advanced multi-cell transmission/reception processes helps in increasing frequency efficiency and cell edge user throughput Estimation unit Calculation unit Determination unit Feedback unit
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Enhanced Multi-antenna Transmission Techniques 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 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
Peak data rates up to 1Gbps are expected from bandwidths of 100MHz. OFDM adds additional sub-carrier to increase bandwidth
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Conclusion
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