LTE Enhancement

NTT DOCOMO, INC., Copyright 2012, All rights reserved. 1
Further LTE Enhancements
toward Future Radio Access
Takehiro Nakamura
NTT DOCOMO, Inc.

LTE Release 10/11 (LTE-Advanced)
Standardization

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-AdvancedITU-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

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

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

Future Radio Access
(LTE Release 12 and Beyond)

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

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:

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

Other Requirements (1)
Mobility
Data rate
1 Gbps
wide area
10 Gbps
peakIMT-Advanced
van diagram
Mobility
Data rate
100 Mbps
wide area
1 Gbps
peakIMT-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

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

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?

Technologies Related to Efficient
Spectrum Extension and Utilization
Spectrum
extension
Capacity

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 ?

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

Technologies for Efficient Support of
Denser Network Deployments
Capacity

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

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

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

Technologies for Further Enhancing
Spectrum Efficiency
Spectrum
efficiency
Capacity

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)

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 #4Enhanced
efficiency
Static DL/UL
allocation
Dynamic DL/UL
allocation

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)

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

LTE Enhancement

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