1 ieee comsoc ft worth & dallas dlt © 2012 mischa dohler mischa dohler cttc, spain ieee comsoc...
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1 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Mischa DohlerCTTC, Spain
IEEE ComSoc Distinguished Lectureship TourFt Worth & Dallas ComSoc Chapters
19 November 2012Slide template is copyright of BeFEMTO. All rights reserved.
Femtocells: Technologies, Standards
and Applications
3 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Smartphones Cause Capacity Crunch
© Thierry Lestable, Sagemcom
home homeoffice
80% Indoors20% Outdoors
4 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
The Resulting Capacity Demand Prediction
© Thierry Lestable, Sagemcom
Total worldwide mobile traffic by 2020: more than 127 exa-bytes (10^18) more than 30 times increase compared to today
Total mobile traffic (EB per year)
-
20.00
40.00
60.00
80.00
100.00
120.00
140.00
2010 2015 2020
Yea
rly
traf
fic
in E
B Europe
Americas
Asia
Rest of the world
World
Source: IDATE
5 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
IMT-A 4G capacity targets [ITU-R M.2133]: 2.2b/s/Hz for downlink and 1.4b/s/Hz for uplink in urban deployment supported rate is thus maximal 100Mbps/km2 (500m cell size; 40MHz)
Capacity needs (reality check): peak density of 8,000 people/Km2 of which only 10% subscribe to the broadband service of which only 20% require access at the same time each requiring 5Mbps
4G requirements … … were short by a factor of 10 yesterday … are short by a factor of 50 today … will be short by a factor of 100 tomorrow
City Average People/Km2
Athens 5,400
Madrid 5,200
London 5,100
Barcelona 4,850
Warsaw 4,300
Naples 4,100
Berlin 3,750
Paris 3,550
Vienna 3,400
8,000 X 10% X 20% X 5Mbps = 800 Mbps/Km2
Are we prepared to meet this capacity demand?
6 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Addressing Capacity Needs in the Past
Increase in capacity over past decades: Martin Cooper: doubled every 30 months over past 100 years overall: million-fold increase in capacity since 1957
Breakdown of these gains: 5 x PHY; 25 x spectrum; 1600 x reduced cells, 5 x rest
Breakdown of (estimated) cost:
Reduced Cells MHz
Reduced Cells MHz PHY
[HOT - TOP 3 IEEE DOWNLOAD IN APRIL 2011] Mischa Dohler, R.W. Heath Jr., A. Lozano, C. Papadias, R.A. Valenzuela, "Is the PHY Layer Dead?," IEEE Communications Magazine, vol 49, issue 4, April 2011, pp 159-165.
Ratio Gain/CostMost Important!
7 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Trend confirms: Link-Layer won’t help
© Avneesh Agrawal, Qualcomm
8 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Time for Major Design Changes
To facilitate the exponential capacityincrease, dramatic changes to how
we design cellular systems are needed!
… oh, and, yes, spectrum is not a problemand power efficiency neither …
9 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Going 5G: Change in Design Paradigms
1. Differentiate clearly between outdoors and indoors design
20% of time 80% of time
Similar data experience outdoors & indoors important!
10 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Going 5G: Change in Design Paradigms
2. Put most efforts on architecture and management thereof
11 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Going 5G: Change in Design Paradigms
3. Acknowledge heterogeneous nature of wireless arena
12 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Going 5G: Change in Design Paradigms
4. Use absolute area capacity rather than spectral efficiencies
heterogeneous spectrum use users care about rates
13 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Going 5G: Change in Design Paradigms
5. Cost considerations must be taken into account at design phase
14 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Outline of Talk (all very high-level!)
A. Indoors Femtocell B. Manage Through SON
16 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
The Small-Cell Solution Space
Only viable solution is via change in architecture & smaller cells: Remote Radio Head: “dumb” radio extension of BS; often RF/IF/BB-over-fiber Relay: wireless radio extension of BS; often limited intelligence Pico Cell: intelligent BS; owned, planned and placed by operator Femto Cell: intelligent BS; mostly owned and placed by consumer; no planning!
© Josep Vidal, UPC
17 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Definition & Differentiation Of Femtocell
Femtocell Picocell Wifi
Site Rental customer operator customer
Installation customer operator customer
Electricity Bill customer operator customer
Radio Planning no (local) yes (prior & global) no
Backhaul Connection via customer dedicated via customer
Macrocell Interaction not (yet) yes not applicable
Transmission Power < 23dBm 23-30dBm 20dBm
Access Rights mainly closed public closed
Handover possible yes vertical
Photo
©Sagem, TID © bandaancha.eu© 3g.co.uk
18 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
The Femtocell Opportunity
)))
Energy
Security
Comfort
Health
Ethernet
WiFi
3G/LTE
FMC & Multimedia
Micro-generationMicro-generation
ADSL, FTTH, …
1. Smart Digital Home:
2. Reduces Customer Churn:
3. Allows Traffic Offload:
4. Energy Saver For All:
© Thierry Lestable, Sagemcom
© Femto Forum, Thierry Lestable, Sagemcom
© Femto Forum, Thierry Lestable, Sagemcom
© Mobile VCE, D. Laurenson
19 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Finding Femtocells Very Appealing
© Femto Forum
20 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Femtocell Technology Providers
The ecosystem is now mature enough© Thierry Lestable, Sagemcom
21 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Femtocell Rollouts & Deployments To-Date
36 commercial deployments in 23 countries15 roll-out commitments in 2012
22 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Femtocells Business Model
In BeFEMTO, four business cases are investigated:
- One off fee: the user pays 50€ once, and the monthly payment does not change (35€/month)
- No fee: the user does not pay for the femtocell, and the monthly payment does not change (35€/month)
- Decrease: the user does not pay for the femtocell, and the monthly payment decreases by 5€ to 30€/month
- Increase: the user does not pay for the femtocell, and the monthly payment increases by 5€ to 40€/month
32$/month
159$ one off
250$ one off
5$/month
255$ one off+42$/month
free of charge
10$/month
180$ one off+1.5$/month
199€ one off10€/month15€/month
100€ one off+8€ /month
50£ one off+5£/month
© BeFEMTO
23 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Femtocell Market Growth Forecast
© Informa Telecoms & Media© Thierry Lestable, Sagemcom
24 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Related Fora & Standards Bodies
Small Cell Forum (before Femto Forum) not-for-profit, founded 2007, rebranded 2012 manufacturer-driven main driver behind femtocell uptake
3GPP IWLAN & EPC standards (for Non-3GPP Access & Mobility) H(e)NB standards (for Basic FemtoCells) LIPA & SIPTO standards (for Local Access & Offloading) ANDSF Standards (for Discovery, Selection & Policy) LIMONET (for LIPA Mobility), SaMOG(for Trusted WiFi), BBAI (for Broadband Network interworking)
IEEE/WFA/WBA Hot Spot 2.0 (Discovery & Seamless Access Control)
GSMA WLAN Task Force (2003?) WiFi Offload White Paper, April 2010 GSMA-WBA Joint Task Force –WiFi Roaming White Paper, Jan 2012
© Prabhakar Chitrapu, InterDigital
25 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Femtocell Design Challenges
1. Low Device Cost: efficient, low-cost power amplifiers, highly sensitive receivers, flexible channel bandwidth, reliable RF
filters; low cost and low power implementation; etc.
2. System Interference Management: minimize interference to macro (and vice versa); minimize interference to adjacent femtos; coping with
unplanned rollouts; coverage estimation, interference cancellation; etc.
3. Femtocell Capacity Maximization: link and access management (handover, admission control, resource management, load balancing and
flow control); dynamic bandwidth allocation and sharing; etc.
4. Backhaul Issues: wired or wireless backhaul, reducing signaling load, QoS provisioning and traffic priorization, joint access
and backhaul design; etc.
5. Viable System Architecture: control & data planes, access control, authentication, local breakout, efficient forwarding, seamless
mobility, zero-config, etc.
© BeFEMTO
26 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Problem Of Interference With Femtos
Source: Zubin Bharucha, DOCOMO Euro-Labs
27 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Rel-10 ICIC In Heterogeneous Networks
To support femtocell deployment effectively, inter-cell interference coordination (ICIC) is necessary
Different from homogeneous network (macrocell deployments), o Low power nodes (femto eNBs) must mute (or reduce transmission
power) Named as “Protected resources” hereo High power nodes (macro eNBs) need not muteo Named as “Non-protected resources” here
Protected/Non-protected resources are multiplexed in frequency or time-domain Both ICIC techniques are effectively supported in Rel-10
Cell layer
Time
Frequency
Femto layerMacro layer
Frequency-domain ICIC
Ca
rrie
r#
1C
arr
ier
#2
Frequency
Time
Cell layer
Time-domain ICIC
Ca
rrie
r #
1
Source: Zubin Bharucha, DOCOMO Euro-Labs
28 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
LTE-A Control & Data Frame Structure
• data region interference mitigation (a lot of work with viable solutions)• control region interference mitigation (surprisingly little work given it is
the actual problem since no control means no data)Source: Zubin Bharucha, DOCOMO Euro-Labs
29 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
LTE-A Detailed Control Frame Structure
• The control region contains 3 control channels:– PCFICH: control frame indicator; occurs only on first OFDM symbol;
scattered in frequency domain; indicates size of control region– PDCCH: downlink control channel; spread in time and frequency;
carries scheduling information– PHICH: HARQ indicator channel; spread in time and frequency;
contains HARQ information• Focus on the performance of the first two because of differences in their
distribution patterns – the PCFICH has restricted positions in the time domain, whereas the PDCCH is dispersed in the time and frequency domains
Source: Zubin Bharucha, DOCOMO Euro-Labs
30 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
LTE-A Control Interference - Current Approaches
(a) •No coordination
Heavy interference on 2 OFDM symbols
(b)• Femto control channel sparseness
Interference to first OFDM symbol is lowered
(c) •Almost blank subframe
Only interference from reference symbol
Femto data transmission is not allowedSource: Zubin Bharucha, DOCOMO Euro-Labs
31 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Novel Femto-Macro ICIC Approach [1/4]
The proposal from DoCoMo Euro-Labs advocates carefully selecting the Physical Cell Identifier (PCI) of HeNBs at start-up, such that any interference caused by their control channels to the PCFICH of any trapped macro UEs is avoided.o In order for this to be possible, the HeNB needs to identify the eNB that it is
closest to. Identifying the eNB means that the HeNB must be aware of the PCI of the eNB
(decoded using synchronization procedure).
Illustration onlySource: Zubin Bharucha, DOCOMO Euro-Labs
32 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Qualcomm Proposition in BeFEMTO for Resource Partitioning in Space for Femto-Macro Interference Mitigation:
Problem Statement: proper resource partitioning is a must to handle femto-macro interference beam selection in MIMO-enabled femto BS equipment could be made use of
Innovative Proposition: design of suitable coordinated beam selection algorithm following LTE codebook designs comparative study between different restriction and codebook policies study outcomes: codebook restrictions yields gains to macro users at low femto capacity loss
Novel Femto-Macro ICIC Approach [4/4]
50% improvement @ macro
5% deterioration @ femtoSource: Qualcomm, BeFEMTO
34© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
Capacity-Optimal Schedule?
With femtocells, the degrees-of-freedom (DOF) increase significantly – and with it complexity! [presented by Interdigital: Globecom’11 – IWM2M, Houston]
35© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
System Degrees of Freedom
High number of femtos/users/resources/etc + interference constraints -> Problem of DOF
Degrees of Freedom (DOF) / Area: new system DOF = old system DOF x 20-30 new system density = old system density x 4 new DOF/km2 = old DOF/km2 x 100
36© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
SON Is The Only Solution
SON Helps For Previously Manual Processes: reduce manual intervention for deployment savings automate repetitive processes examples: automatic planning & self-configuration
SON Helps For Too Fast/Complex Processes: improve run-time operation based on real-time data automate optimization of critical network elements example: self-optimization & self-healing
Among the many possible approaches, we deal with cognitive/docitive RRM to facilitate SON.
39© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
From cognitive to docitive networking paradigms: cognition: “system which is working under conditions it was not designed for” docition: “teaching” between expert nodes to accelerate learning/cognition result: truly autonomous SON with quick convergence
SON Through Cognition/Docition
40© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
Cognitive Approach – Q-Learning
...
...
1s
2s
ks
11 pa ll pa
),( 11 asQ ),( 1 lasQ
),( 12 asQ ),( 2 lasQ
),( 1asQ k ),( lk asQ
...
v ),( 1avQ ),( lavQ
),( *2 asQ
),( *avQ
... ...
... ...
FOR each (s, a) DO
Initialize table entry: Observe current state s
WHILE (true) DO
Select action a and execute it
Receive immediate cost c
Observe new state v
Update table entry for Q(s,a) as
follows
State transition from s to v
0),( asQ
)],(),(max[),(),( asQavQcasQasQa
41© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
Nodes operate in a distributed and autonomous fashion but exchange suitable parts of their Q-Table:
Docition Approach – Exchange of Q-Entries
Input State
Output Action
pxy
Startup Docition. Docitive femto BSs teach their policies to newcomers joining the network.
IQ-Driven Docition. Docitive radios periodically share part of their policies with less expert nodes with similar gradient.
42© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
Macrocell capacity as function of femtocell density:
Performance – Superior Capacity
43© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
CCDF of average SINR at macrouser for a 50 % occupation ratio:
Performance – Superior Convergence Precision
44© 2012 Mischa Dohler IEEE ComSoc Ft Worth & Dallas DLT
Convergence speed improves by order of magnitude from 20,000 (cognitive) to 4,000 (docitive) iterations:
Performance – Superior Convergence Speed
46 IEEE ComSoc Ft Worth & Dallas DLT© 2012 Mischa Dohler
Conclusions on Femto Cells
Heterogeneity Is Quickly Increasing:femtos, networked femtos, wifi, m2m, etc, etcfuture use outdoors, mobile, in relay formallow for viable QoS/QoE delivery
Self-Organizing Networking Will Be Key:distributed localized SON (important for signaling) standards compliant SON approaches for industry uptaketake energy constraints into account
Business Models subscriber models FON-like approaches