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Further LTE Enhancements toward Future Radio Access
Takehiro Nakamura NTT DOCOMO, Inc.
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LTE Release 10/11 (LTE-Advanced) Standardization
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3GPP仕様のリリース 1999 2000 2001 2002 2003 2004 2005
Release 99
Release 4
Release 5
Release 6
1.28Mcps TDD
HSDPA
W-CDMA
HSUPA, MBMS
2006 2007 2008 2009
Release 7 HSPA+ (MIMO, HOM etc.)
Release 8
2010 2011
LTE
Release 9
Release 10
GSM/GPRS/EDGE enhancements
Minor LTE enhancements
2012 2013
Release 11
ITU-R M.1457 IMT-2000 Recommendation
LTE-Advanced ITU-R M.2012 IMT-Advanced
Recommendation
Approved at ITU-R RA in Jan. 2012
3GPP TSG-RAN Workshop on Release 12 onward to be held on June 11-12, 2012
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Key Requirements for LTE-Advanced
March 4, 2011
• LTE-Advanced shall be deployed as an evolution of LTE Release 8 and on new
bands. • LTE-Advanced shall be backwards
compatible with LTE Release 8 Smooth and flexible system migration
from Rel-8 LTE to LTE-Advanced
LTE Rel-8 cell
LTE Rel-8 terminal LTE-Advanced terminal
LTE-Advanced cell
LTE Rel-8 terminal LTE-Advanced terminal
LTE-Advanced backward compatibility with LTE Rel-8
An LTE-Advanced terminal can work in an LTE Rel-8 cell
An LTE Rel-8 terminal can work in an LTE-Advanced cell
LTE-Advanced (LTE Release 10)
LTE Release 8
LTE-Advanced contains all features of LTE Rel-8&9 and additional features for further evolution
LTE Release 9
LTE-Advanced evolved from LTE Rel-8
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Key Features in LTE Release 10&11 Support of Wider Bandwidth(Carrier Aggregation) Rel-10&11
• Use of multiple component carriers(CC) to extend bandwidth up to 100 MHz • Common physical layer parameters between component carrier and LTE Rel-8 carrier Improvement of peak data rate, backward compatibility with LTE Rel-8
Advanced MIMO techniques Rel-10 • Extension to up to 8-layer transmission in downlink • Introduction of single-user MIMO up to 4-layer transmission in uplink • Enhancements of multi-user MIMO Improvement of peak data rate and capacity
Heterogeneous network and eICIC(enhanced Inter-Cell Interference Coordination) Rel-10&11
• Interference coordination for overlaid deployment of cells with different Tx power Improvement of cell-edge throughput and coverage
Relay Rel-10 • Type 1 relay supports radio backhaul and creates a separate cell and appear as Rel-8
LTE eNB to Rel-8 LTE UEs Improvement of coverage and flexibility of service area extension
Coordinated Multi-Point transmission and reception (CoMP) Rel-11 • Support of multi-cell transmission and reception Improvement of cell-edge throughput and coverage
Interference rejection combining (IRC) UE receiver Rel-11 • Improved minimum performance requirements for E-UTRA Improvement of cell-edge throughput
100 MHz
f CC
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Future Radio Access (LTE Release 12 and Beyond)
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Growth of Packet Traffic in DOCOMO • Various services, especially video services, and high-speed mobile access
increased amount of mobile data traffic – Approx. 1.6 times per year (2004 – 2009) – Approx. 2 times per year (2010-2011)
• Further traffic growth is projected due to dramatic increase in Smartphone sales
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By 2015, the mobile data traffic footprint of a single subscriber could be 450 times what it was 10 years earlier in 2005.
Forecast of Mobile Data Traffic Growth
Mobile video has the highest growth rate of any application category
Cisco VNI Mobile:
Consensus in the industry is that there will be substantial growth in demand for mobile data traffic over the next 5 – 10 years
UMTS Forum:
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Approach for Capacity Enhancements
Spectrum extension
Network density
Required capacity (bps/km2 = bps/Hz/cell x Hz x cell/km2)
Spectrum efficiency
Current capacity
New cellular concept for cost/energy-efficient dense deployments
Non-orthogonal multiple access
Study for new interference scenarios
Dense urban Shopping mall
Home/office
Cellular network assists local area radio access
Hybrid access using coverage and capacity spectrum bands
Multiple access technologies with Tx-Rx cooperative
interference cancellation
Traffic offloading (alternative means for communication)
WiFi offload, D2D, etc.
We need set of radio access technologies to satisfy future requirements of 500-1000x capacity
Existing cellular bands Higher/wider frequency bands
Frequency
Very wide Super wide
Controller
TRx
TRx
TRx
TRx
TRx
TRx
TRx
TRx
Massive MIMO, Advanced receiver
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Other Requirements (1)
Mob
ility
Data rate
1 Gbps wide area
10 Gbps peak IMT-Advanced
van diagram Mob
ility
Data rate
100 Mbps wide area
1 Gbps peak IMT-Advanced
van diagram
10x improvement in the next decade More spectra utilized efficiently
Requirements mainly from user perspective
Source: Artist4G (FP7 ICT), Jan. 2010
• Higher data rate and user-experienced throughput
– Data rate competitive to that of future wired networks
• Gbps-order experienced throughput
– Low latency for improving user experience
• Fairness of user throughput
– In a cell • Improve cell-edge throughput
– Among cells • Urban to rural • Digital divide
– Among users • Lower system impact from few
heavy users
Gbps-order experienced throughput
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Other Requirements (2)
• Flexible, easy, and cost-efficient operation
– For diverse spectrum allocation • Efficient utilization of
higher/wider frequency bands – For diverse environments and
network nodes/devices with different types of backhauling
• RRE, Femto, relay, etc. – For diverse types of services, user
devices, and communication methodologies
• MTC, thin client, etc. • Energy saving (Green)
– Reduction in joule per bit • System robustness against
emergencies – Earthquake, Tsunami, etc.
Requirements mainly from operator perspective
Different duplex schemes may be applied
Frequency
Non-contiguous spectrum allocation over wide range of frequencies
Macrocells RRE Femto
Robustness to emergencies
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Possible Standardization Scenario • Standardization scenario towards 2020
– Mid-to-long term evolution introducing new technologies to achieve required capacity gain based on 3GPP LTE radio interface
– The following two types of evolutions to be considered
• Backward-compatible evolutions – Evolutions backward compatible to legacy UEs sharing the same spectrum bands – New technologies to be introduced, e.g., for further improving spectrum efficiency
• Most of new radio access technologies can be introduced in future LTE releases using LTE (OFDM/SC-FDMA) based signal waveform
• Complementary evolutions – Introduction of new carrier type that is complementary to legacy carrier type(s) with
backward-compatible evolutions – Evolutions focusing on new frequency spectrum bands and/or specific scenarios
such as enhanced local area radio access
Rel. 8 Rel. 10
Rel. 1X
Rel. 11 Rel. 1X
Legacy carrier type Rel. 11 Rel. 1X
Additional carrier type
New carrier type or new radio inter face
Complementary evolutions
Backward-compatible evolutions
New RAT?
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Technologies Related to Efficient Spectrum Extension and Utilization
Spectrum extension
Capacity
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Wider Bandwidth • Super-wideband to achieve “Gbps” as typical data rate
At least more than 200 MHz will be desirable (maybe up to 1 GHz)
• Utilization of much higher frequencies – Maybe possible to find contiguous wideband spectrum in higher frequency
Bandwidth Spectrum efficiency 100 MHz 10 bps/Hz (4x4 MIMO) 200 MHz 5 bps/Hz (2x2 MIMO) 300 MHz 3.3 bps/Hz (~64QAM) 600 MHz 1.7 bps/Hz (~16QAM) 1000 MHz 1 bps/Hz (~QPSK)
Examples to achieve 1-Gbps data rate
FRA Gbps to be achieved with lower spectrum efficiency, e.g., without MIMO (More than 10-Gbps can be achieved by MIMO technology)
LTE-A
Existing cellular bands Higher frequency bands
Frequency
Very wide (e.g. > 3.5GHz)
Super wide (e.g. > 10GHz)
How to use in cellular systems ?
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Efficient Spectrum Utilization • Hybrid radio access using lower & higher frequency bands
– Basic coverage/mobility supported in lower frequency bands, e.g., existing cellular bands
• Current Service Quality in terms of Connectivity/ Mobility can be maintained • Support control signaling for efficient small-cell discovery
– High speed data transmission supported in higher frequency bands • Large bandwidth • Mainly for smaller or denser cell deployments
Existing cellular bands (high power density for coverage)
Higher frequency bands (wider bandwidth for high data rate)
Frequency
Very wide (e.g. > 3.5GHz)
Super wide (e.g. > 10GHz)
Hybrid radio access
Macro-cellular deployments supporting full coverage area
Various local area scenarios with low-power nodes/devices
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Technologies for Efficient Support of Denser Network Deployments
Capacity
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Requirements for Denser Network Deployments
• Capacity per NW cost (bps/cost) = Capacity per unit area / NW cost per unit area
• Efficient small cell identification & mobility – UE battery saving
• Can be optimized to low mobility – Support for non-uniform deployments
• Dense cells for high traffic area • Less efforts on cell planning
(bps/km2 (= bps/cell x cell/km2))
km
km
(cost/km2) Spectrum efficiency x bandwidth
- Low cost NW node & backhaul deployments
- Easy cell planning & maintenance - NW energy saving
Macro cell
Small cell
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Deployment Scenarios • Two deployment scenarios are identified for small-cell
deployments (increasing network density): – Scenario 1 (Mixed deployment scenario):
• Small cell and Macro cell co-exist on a single carrier.
– Scenario 2 (Small-cell dedicated carrier scenario): • Small cell utilizes a dedicated carrier, where no Macro cell exists.
F1
F2
F0
Scenario 1: Mixed deployment scenario Scenario 2: Small-cell dedicated carrier scenario
Secenario 1 was studied in Rel-11. We assume Scenario 2 getting more and more important in Rel-12 onward
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RRH CA Deployments
2 GHz (Example)
3.5 GHz (Example)
Macro cell
Macro cell link can maintain good connectivity and mobility
RRH link can provide high throughput due to frequency reuse using small RRH cells
Additional carrier type for RRH link would provide more flexible and cost/energy-efficient operations
RRH
RRH
RRH
RRH
RRH link
Macro cell link
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Technologies for Further Enhancing Spectrum Efficiency
Spe
ctru
m
effic
ienc
y
Capacity
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Different Requirements Between WA and LA Spectra
• Different requirements for radio access between Wide Area (WA) and Local Area (LA) spectra in HetNet deployments – But, commonality between WA and LA to be considered within a
framework of LTE-based radio interface
Macro-cellular deployments supporting full coverage area
Various local area scenarios with low-power nodes/devices
Wide Area spectrum Local Area spectrum Spectrum efficiency Very important
(limited BW) Important (may not be critical if large BW available)
Mobility Medium-to-High Low Coverage Essential Not critical
(but wider is better) DL/UL radio link Asymmetric More symmetric Traffic load More uniform
(many users & cell planning) More fluctuated (less users & non-uniform deployments)
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FDD/TDD in Local Area • FDD is advantageous over TDD in wide area
– No need for synchronization among cells/operators • The adjacent channel interference is much lower than in TDD
– Wider coverage and lower latency owing to continuous transmission • DL/UL channels are always "open“
• TDD might be more applicable in local area & in higher frequency bands – Requirements on synchronization among operators can be relaxed in local area – Potential benefits in spectrum sharing between DL/UL – Dynamic TDD
• Traffic is more bursty (unbalanced DL/UL) in local area • Interference management of DL/UL transmissions is required among multi-points
– Possibly facilitate worldwide harmonized spectrum allocation • Flexible spectrum allocation • No need for guard band (No need for duplexer)
UL DL
UL DL
UL DL
UL DL
DL UL
DL DL
User #2 User #1
User #3 User #4
User #2 User #1
User #3 User #4 Enhanced
efficiency
Static DL/UL allocation
Dynamic DL/UL allocation
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Concept of Hybrid Radio Access • Hybrid radio access
– Adaptation of radio access schemes according to environments, spectrum bands, types of traffic, etc.
• Required high commonality in radio interface among radio access schemes
• Example of hybrid access schemes – Hybrid FDD and TDD according to cell environments – Hybrid non-orthogonal and orthogonal multiple access schemes
according to, e.g., path loss variation among users
– Hybrid multi-carrier and single-carrier transmission schemes according to, e.g., required coverage or cell environments
Wide area/lower frequency Local area/higher frequency
Adaptation for radio access schemes
Resource mapping & Power control
DFT (SC)
S/P (MC) Tx data IFFT Transmission
Local area
Wide area
freq/time Orthogonal
freq/time Non-orthogonal
Path loss variation Large Small (Wide area) (Local area)
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Conclusion • LTE Release 10 and 11
– LTE Release 10 was developped and approved in ITU-R M.2012 as LTE-Advanced
– LTE Release 11 is under development to enhance LTE Release 10 technologies
• Future Radio Access (LTE Release 12 and beyond) – 3GPP will hold a Workshop on Release 12 onward to identify
requirements and potential technologies for Future Radio Access – Variety of requirements including reduced cost and further capacity
enhancements needed by traffic explosion – Two evolution scenarios, backward compatible evolution and
complementary evolution, to satisfy both of backward compatibility and sufficient gain
– Key techniques to meet requirements • Efficient utilization of higher and wider spectrum bands • New small-cell dedicated carrier for efficient and simple NW densification • Hybrid Radio Access for wide area and local area enhancements
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