valentin gheorghiu - jst · hyper-dense cells and more spectrum over macro-only deployment 0 250...
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Heterogeneous networks for dependable wireless access
and the 1000x capacity challenge Valentin Gheorghiu
PAGE 2
• Why 1000x?
• How to achieve 1000x?
• Heterogeneous networks and challenges
LTE-Adv Rel.10/11 eICIC/FeICIC (ICIC=Inter-cell interference coordination)
Mobility challenges and dependability
Hyper dense HetNets
– Network management with UltraSON
Future mobility challenges
RF challenges
• Concluding remarks
Summary
PAGE 3
Strong Mobile Data Demand
0
6
12
2011 2012 2013 2014 2015 2016
Ex
ab
yte
s p
er
Mo
nth
Overall Mobile Data Traffic Growth
NETWORK CAPACITY CHALLENGE!
0.6 EB 1.3 EB
4.2 EB
2.4 EB
10.8 EB
6.9 EB
being planned
by operators
over next decade
PAGE 4
Capacity increases enable by topology changes
Evolved 3G (EV-DO Rev. B & HSPA+)
Data optimized 3G (EV-DO & HSPA)
3G (IMT-2000): Voice & Data (e.g. CDMA2000 1X & WCDMA)
2G: Voice Capacity (Digital e.g. GSM & IS-95)
1G: Voice (Analog e.g. AMPS)
Next Generation
Leap
Next Generation
Leap
Next Generation
Leap
Radio link
approaching
theoretical limit
LTE (OFDMA)
Different dimension of improvement:
adding small cells like picos and
femtos and mitigate interference
Bring network closer to users and
leverage Hetnets1—add small
cells—for next leap in performance
1Leveraging heterogeneous network topology: macro network with added small cells like picocells and femtocells (cells
with different transmit power)
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We Can Reach The Air Link Limit—Shannon’s Law
Still ways to improve system capacity
Capacity ≈ n W log2(1+ ) Signal
Noise
Number of
Antennas
More
Spectrum E.g. Mitigate
interference
Qualcomm proprietary and confidential
PAGE 6
The Biggest Gain—Re-Use Shannon’s Law
Capacity ≈ n W log2(1+ ) Signal
Noise
Number of
Antennas
More
Spectrum E.g. Mitigate
interference
Qualcomm proprietary and confidential
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• Conventional cell splitting is an inefficient way to address non-uniform and exploding data demand
In addition, site acquisition is difficult and cells already approaching lower limits of site to site distance
Heterogeneous Networks - Overview
Heterogeneous deployments with eICIC1 and feICIC1
(LTE Rel.10/11)
Hyper Dense Heterogeneous deployments with Small Cells (LTE Rel.12~)
Homogeneous deployments (Macro
only, e.g. LTE Rel.8)
Co-channel deployment
Cell Range Expansion
Adaptive Resource
Partitioning
Almost blank subframes
Advanced receivers with
interference cancelation
More spectrum (higher frequency
bands, e.g. 3.5GHz~)
Dual connectivity
Self Organizing Networks (UltraSON)
Femto Pico
Pico
Pico Macro
1 ICIC=Inter Cell Interference Coordination, e=Enhanced, Fe=Further Enhanced
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• Resources between macro BS and low power BSs split in the time domain
• Range Expansion increases footprint of co-channel Picos/Femtos
Allows more UEs to be served by low power BSs
More equitable distribution of capacity among Macros and Picos/Femtos
• Full Range Expansion can be supported in LTE-Advanced
Large bias to compensate the power difference between Macro and Pico
Enabled by resource partitioning and enhanced UE receiver
Heterogeneous Networks and Cell Range Expansion
Macro
Limited footprint of Picos due to Macro signal
Pico Macro Pico Pico Pico
Increased footprint of Picos when Macro
frees up resource
In subframes reserved for Picos In subframes reserved for Macros
Example:
Semi-static allocation 50%
Macro and
50% Picos
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• Mobility performance is extremely important from a network dependability point of view
• Number of handovers is expected to increase because of the increase in the number of cells
Mobility management becomes a problem
• Simulation results show big increase in the number of handover failures, specially in certain scenarios (e.g. Pico-Macro)
System simulation based on scenarios used in 3GPP
Mobility Challenges and Dependability (1)
Simulation assumptions
• 30km/h
• Macros deployed at 500m distance
• 30picos/macro cell
• Fully loaded system
• HO Failure based on service outage
(device goes into link failure) 0
10
20
30
40
50
60
Baseline (No eICIC) Rel.11 9dB CRE w/ resourcepartitioning
Handover Failures (%)
Macro-Macro
Macro-Pico
Pico-Macro
Pico-Pico
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• CRE and resource partitioning help mitigate some of the mobility problems
• Pico-Macro HO is more likely to fail than Macro-Pico HO
The Pico signal strength varies fast because of shadowing and much lower antenna height
Sudden change in the Pico’s signal due to mobility would introduce similar challenge for both inbound mobility and outbound mobility
However, only a small fraction of Macro-Pico handovers go through the outage area
On the other hand, all outbound handovers are subject to link failure because of strong interference from the macro
Mobility Challenges and Dependability (2)
• Mitigation Techniques
Different HO parameters for different cell types
Differentiate devices based on speed ⇒ high speed devices kept only on macro cell
• Devices have little freedom as mobility is driven by the network
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• More capacity improvements than what is offered by LTE Rel.10/11 will be needed to fulfill 1000x
• Hyper densification is likely to be the key to reach 1000x capacity increase
Small cells deployed in higher frequency bands
Hyper Dense HetNets
METRO
RESIDENTIAL
ENTERPRISE
USER DEPLOYED
Typically indoor small cells
OPERATOR DEPLOYED
Indoor/outdoor small cells1
Extreme Densification—Small Cells Everywhere
4G Relays
& Wireless
Backhaul
1 Such as relay and Pico/Metro/RRH small cells for hotspots. RRH= Remote Radio Heads, in addition Distributed Antenna Systems are used in HetNets
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• Network management has to be automated such that deployment is scalable⇒ Self Organizing Networks(SON) techniques will be very important
• Basic SON features standardized from Rel.8 (e.g. ANR)
Hyper Dense Hetnets – Network management
Self Configuration: Automatic cell
parameter and backhaul config.
• Automatic Cell ID (PCI) selection
• Automatic neighbor discovery (including
3GPP ANR)
Backhaul Aware Operation:
Handle backhaul constraints • Backhaul quality aware load balancing
Category UltraSON Features
Mobility Management: Optimize
HO performance and reduce
signaling load
• Frequent Handover Mitigation
• Forward handover
• Robust mobility (including 3GPP MRO)
Dynamic Resource and Tx Power
Management: Optimize capacity,
minimize pilot pollution and load
balancing
• Tx power management
• Resource partitioning and coordination
(including 3GPP ICIC)
• Load balancing
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• Mobility management will be more challenging because of the increase in number of cells and frequencies
• Dual connectivity will be one of the solutions
Devices are connected to a Macro cell and a small cell at the same time
The control information(including mobility control) will be transmitted on the Macro layer
Connectivity is maintained on the macro cell while the small cells are used opportunistically for traffic offload
Increase overall dependability
Hyper Dense Hetnets – Mobility and Dependability
• Mobility state detection
Network can make “smart” decisions on whether to handover a device to a small cell based on its mobility
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• Higher spectrum bands suitable for small cells
• To achieve the needed increase in capacity more spectrum will be needed
RF circuits will have to support a very wide range of frequency bands
– 450MHz~60GHz
Broadband processing for carrier aggregation
– ~100MHz bandwidth
RF Challenges – Dependable RF
~450 MHz
60GHz
~3GHz
Very High Bands
enable Access In
Every Room
Wide Area
Spectrum
INDOOR
HOTSPOT
3.4 to 3.8 GHz Emerging as a new
small cell band
PAGE 15
Is 1000x really possible?
A SCALABLE APPROACH TO MEET THE 1000X CHALLENGE
Downlink Median Throughput Gain* Hyper-dense cells and more spectrum over Macro-only deployment
0
250
500
750
1000
1250
1500
0 72 144 216
1000x Capacity Gain Using 144 Small Cells Per
Macro and 10x Spectrum**
Number of Small Cells Per Macro
x
x
x
x
x
x
36
* This example shows one possible combination of small cells and spectrum to achieve 1000x capacity gain. ** Macrocells use 10MHz spectrum in 2GHz and small cells use 100MHz spectrum in 3.5GHz, 200 active users per macro cell.
Re
lati
ve C
apac
ity
Gai
n
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• Mobile Data Traffic is expected to grow 1000x over the next 10 years
• Dependable networks that deliver the data timely and maintain seamless connectivity are required
• Heterogeneous network deployments will be the key to meeting the data traffic demand
Rel. 10/11 Hetnets enabled through resource partitioning and advanced receivers
Hyper Dense Hetnets with small cells on higher frequencies, dual connectivity
• Dependable RF circuits able to process frequencies up to 60GHz will be needed
Spectrum from 450MHz up to 60GHz will be used, small cells are very likely to be deployed in the higher frequency bands
RF circuits capable of processing up to 100MHz bandwidth will be required for carrier aggregation
Concluding Remarks
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Thank You
Will There Be 1000x Demand? It’s Just a Matter of Time…