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2014/3/11
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5G: A Paradigm Shift of Cellular Networks
Electronic Engineering, Tsinghua UniversityTsinghua National Lab for Information Science and Technology
March 7, 2014
Zhisheng Niu
Tokyo Wireless Technology Summit 2014
Migration of Mobile Communications
• Cooper’s Law: “The data rate available to a wireless device doubles roughly every 30 months” (Martin Cooper)– This has held for over 50 yrs, leading to 1,000,000x increase – Technology: 1G (’80s) 2G (’90s) 3G (’00s) 4G (’10s)
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“People always over-estimate things for 3 years scope,
but under-estimate things for 10 year scope”
– Bill Gates
What does 5G look like?
What will the enabling technologies be for 5G?
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What’s the technology that mostly contributed to this success?
TDMA? CDMA? AMC? Turbo? OFDM? MIMO? ……
To answer this question, we need understand
25x 5x 5x
1600x
0
500
1000
1500
2000
widerspectrum
dividing thespectrum intosmaller slices
bettermodulationscheme
reduced cellsizes
Wireless Capacity…
Source: William Webb, Ofcom
It’s Cellular!
Cellular was invented for spectrum-efficiency
But, is it really energy‐efficient? Is it smart enough to support massive M2M connections?
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This has not been a major concern
Energy of firewood:16.2 megajoules/kgOnly one bit: invasion or no-invasion
Extremely energy inefficient, yet needed5
But, it is a big concern today
• But, energy consumption and cost increased dramatically – Globally, #BS > 5 million, #Users>5 billion, EC> 100bn KWh (2012)
– As 4G/5G deploys and IoT boosts, EC & Connections grow dramatically
– Energy cost is also increasing (price and environmental impact)
How to carry 1000X traffic and connections using limited spectrum & energy?
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EE as a key decision-making factor
Equipment Type TEEER Formula Min. TEEER Allowable
Transport ‐log (Ptotal / Throughput) 7.54
optical and Video 7.54
P2P Microwave 5.75
Switch/Router ‐log (Ptotal / Forwarding Capacity) 7.67
Media Gateway ‐log (Ptotal / Throughput) 6.54
Access (Access Lines / Ptotal ) +1 2.50
Power (POut Total / PIn Total ) X 10 9.20
Power Amplifier (Wireless)
(Total RF Output Power / Total Input Power) X 10
1.05
Base Station ? ?
Verizon’s TEEER (Telecom Equipment Energy Efficiency Rating) since 2009
www.verizonnebs.com/TPRs/VZ-TPR-9207.pdf
Ptotal = 0.35 x Pmax + 0.40 x P50% load + 0.25 x Psleep
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Smartness was also not an issue, but
Densely and randomly deployed
2G/3G/4G Coexisting (HetNet)
J. Andrews, “Seven Ways that HetNets are Cellular Paradigm Shift”, IEEE ComMag, March 2013 8
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Diversified Needs for 5G
• Mobile traffic will have another exp. growth by 2020– Capacity-hungry video dominates: higher SE and EE (Green)– Control-intensive massive connections access should be Smarter
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5G Cellular: Greener and Smarter
Capacity-oriented
2000
Coverage‐oriented
Traffic Vo
lum
e or E
nerg
y Co
nsu
mp
tion Time
2G
Energy-oriented
2010
3G3G+
4G4G
Traffic Volume
Green&
Smart
2020
Energy Consumption
5G
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LTE‐A
LTE
GREEN
PHY approach only is no more enough
Energy-Spectrum Tradeoff in Wireless Transmissions
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– 1G (’80s): Analog, Voice, FDMA, Macro (Coverage-oriented)
– 2G (’90s): Digital, Voice, TDMA, Macro (Coverage-oriented)
– 3G (’00s): Digital, Data, CDMA, Micro (SE-oriented)
– 4G (’10s): Digital, Video, OFDMA, Pico/Femto (SE-oriented)
– 5G (’20s): Digital, Video/M2M, BDMA?, ????? (SE/EE-oriented)
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5G: A Paradigm Shift of Cellular Architecture
Cell densification is trying to further improve SE, but is it
also good for EE and smart enough to support M2M?
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Energy Waste in Existing Cellular
Traffic data from 319 HSPA cells in a European capital city measured from Jan. 1-22 2009 (Ericsson)
3 sector HSPA Site
1 25 50 75 1000
10
20
30
40
50
60
70
80
90
100
Load [%]
DC
Pow
er C
onsu
mpt
ion
[%]
OtherFans
RU3
RU2
RU1Base band
80% of the BSs are quite lightly loaded for 80% of the time, but still consume (waste) a lot of energy
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Why so many BSs under‐utilized, while still need to be densely deployed in some area?
Existing cellular is neither smart nor green
Why lightly‐loaded BSs can’t be switched off (sleep)?
- Mobile traffic is highly dynamic!
- BSs need to provide data services as well as network coverage simultaneously
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Ways to Reduce Energy Waste
• Exploiting traffic dynamics (reduce energy consumption when traffic is low)
– Targeting THROUGHPUT rather than CAPACITY per joule
• Exploit energy model (much energy is consumed at BB/PA/AC rather than RF, therefore BS sleeping is the most efficient way for energy saving)
– Targeting TOTAL ENERGY rather than RF power reduction only
• Exploit cell collaboration (cell densification and HetNet make cell collaboration possible, helping to turn more BSs off)
– Targeting NETWORK rather than LINK/CELL performance
• GREEN: Globally Resource-optimized & Energy-Efficient Networks
– GREEN should be a holistic approach with paradigm shift
– 5G Cellular networks should be more smart and GREEN
Key idea: Reduce Energy Waste by Adapting to Real-traffic Dynamics (REWARD)
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Tango: Traffic-aware network planning & green operation- Adapted to traffic distribution (temporally and spatially non-uniform) - Adapted to traffic characteristics (unicast, multicast, broadcast)- Adapted to QoS requirements (realtime, nonrealtime)
5G Cellular: Adapt to Traffic Dynamics(Traffic dynamics can provide opportunities for energy saving)
0:00 12:00 24:00
Power
t
Reduced Consumption
Usual Power Consumption (non-adaptive)
Traffic
Key challenge: How to guarantee the coverage and QoS?How to model and predict traffic dynamics?
Z. Niu, “TANGO: Traffic-Aware Network Planning and Green Operation”,IEEE Wireless Commun., Oct.2011 (invited article)
BS Sleep
Power Adaptation
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Example: Cell Zooming
Z. Niu, Y. Wu, J. Gong, Z. Yang, “Cell zooming for cost-efficient green cellular network,” IEEE ComMag, Nov. 2010 (IEEE APB Best Paper Award 2014)
• Cell Zooming for Smart Cellular Network
Central cell zooms in as traffic load increases
Central cell zooms out as traffic load decreases
Central cell sleeps as traffic load getting quite low
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A Dynamic Programing Approach for BS Sleeping
x-axis (m)
y-a
xis
(m
)
500 1000 1500 2000 2500 3000
500
1000
1500
2000
2500
High Load
Medium
Low Load
Active cells
Sleeping cells
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J. Gong, S. Zhou, Z. Niu, “A Dynamic Programming Approach for Base Station Sleeping in Cellular Networks,” IEICE Trans. Commun., Vol.E95-B, No.2, pp.551-562, Feb. 2012
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5G Cellular: Adapt to Environment(BS collaboration can provide opportunities for energy saving)
• CHORUS: Collaborative & Harmonized Open Radio Ubiquitous System– Open Radio: spectrum in HetNet are shared by multi-modal terminals (software defined radio)
– Globally optimized: cross-layer cross-node cross-network/system (software defined network)
cross-netw
ork/systemdesign
cross-layer cross-node design
[1] S. Zhou, Z. Niu, S. Tanabe, “CHORUS: Collaborative and Harmonized Open Radio Ubiquitous Systems”, 4th Intl. Conf. Commun. Sys. & Nets. (COMSNETS), Bangalore, India, Jan. 2012 (invited)[2] S. Zhou, Z. Niu, S. Tanabe, and P. Yang, “CHORUS: Framework for Scalable Collaboration in Heterogeneous Networks with Cognitive Synergy,” IEEE Wireless Commun. Mag, accepted, 2012
Challenges: 1) How to detect the NSI? (information explosion and incompleteness?)2) How to virtualize the network resources? (self-optimizing networks)
HetNet
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Example: BS Sharing
B. Leng, P. Mansourifard, B. Krishnamachari, “Microeconomic Analysis of Base-Station Sharing in Green Cellular Networks”, IEEE INFOCOM 2014, Toronto, Canada, April 2014
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5G Cellular: Deal with the Dilemma
Capacity‐hungry Apps (e.g., mobile videos)
Higher SE
Higher EE
Control‐intensive Apps (e.g., M2M, social networking)
Faster Connectivity
Higher Reliability
?Smaller cells Larger cells
C-plane larger
D-plane smaller
decouple
Less signaling overhead
Global optimization
SmartCoverage-on-demand
Densely deployed
Green21
Hyper Cellular for Green and Smart
• Decouple control and data coverage so that data cells could be more adaptive to traffic dynamics and network state, and control cells can take global optimization
Traffic analysis
Broad
ban
dNarro
wban
d
Signalin
g
Contro
l
GSM
3G
Macro
Micro
Hyper
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Hyper-cellular: Virtual (Elastic) Coverage
Decouple of signaling coverage and traffic coverage
Signaling coverage is seamless and traffic coverage is reconfigurable
Challenge: unified signaling for virtualized cellular NWs
U‐Plane
C‐Plane
Seamless
Elastic
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Technical Challenges
• How to decouple signaling from data coverage? How to integrate the signaling functions of HetNets? – Complete decoupling may lead to new bottleneck and delays due to frequent
visits to signaling-BSs (main difference from BCG2), but which functions should be left into the data-BSs?
• How to guarantee signaling coverage highly reliable? – Need new protocol for S-BSs. Also, tradeoff between reliability and delay
• How to detect user behaviors, QoS requests, terminal capability, and provide services in an EE manner? – Data mining, cognitive radio, on-line learning, …
• How to locate users and associate them to the best D-BS? – The best cells may be in sleeping state, activate or not?
• How to balance the EC of network parts and user terminals? – User terminals need to keep associations with S-BS in a wider scope
• ……Z. Niu, S. Zhou, S. Zhou, X. Zhong, J. Wang, “A Hyper-Cellular Paradigm for Globally Resource-optimized and Energy-Efficient Networks (GREEN)”, Science in China, Sep. 2012 (in Chinese) 24
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Global Research Activities on “5G”
• “BDMA and Relay with group cooperation” (Korea, 2008)
• “5G Communications Research Lab” (Univ. of Dresden, 2012.5)
– Jointly funded by National Instruments
• “₤35m for 5G Research Centre” (Univ. of Surrey, 2012.10)
– jointly funded by UK Research Partnership Investment Fund (UKRPIF) and a consortium of Huawei, Samsung, Telefonica Europe, Fujitsu Laboratories Europe, Rohde & Schwarz, and Aircom International
• “China launched a WG on 5G” (China Academy of Telecom Research, 2012.11)
• “Huawei invests $600m for 10Gbps 5G network” (2013.11)
• “Korea to spend $1.5 billion on 5G mobile network” (2014.1)
• “China Mobile joined NGMN 5G Alliance” (MWC2014, 2014.2)
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Global Research Activities on “5G”
• “€50m EU research grants to develop '5G' technology” (EC, 2013.2)– METIS: Mobile and wireless communications Enablers for Twenty-twenty (2020)
Information Society (SWE Ericsson, 29 partners) specifies 5G should provide 1000X higher mobile data volume per area
10‐100X higher No. connected devices for Internet of Things 10‐100X higher typical user data rate
10X longer battery life for low power M2M Communications 5X reduced e2e latency
– 5GNOW: 5th Generation Non-Orthogonal Waveforms for Asynchronous Signalling (GER)
– iJOIN: Interworking and JOINt Design of an Open Access and Backhaul Network Architecture for Small Cells based on Cloud Networks (ESP)
– TROPIC: Distributed computing, storage and radio resource allocation over cooperative femtocells (ESP)
– COMBO: joint optimisation of fixed and mobile access (GER)
– MOTO: Mobile OpportunisTic Traffic Offloading (FRA)
– PHYLAWS: PHYsical LAyer Wireless Security
• "5GrEEn - Towards Green 5G Mobile Networks“ (EIT ICT Labs. 2013.9) 26
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Green Activities in China
End-to-End Energy Efficient Networks (National 863 Program, 2012~2015)
Green Radio Excellent in Arch. and Tech. (Huawei Program, 2010 ~ )
Globally Resource-optimized and Energy-Efficient Networks (National 973 Program, 2012~2016)
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Some Research Progress in 2012/13
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How much energy can be saved by Separation?
Traditional Cell Hyper Cell
in outP k P b
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How much energy can be saved by separation?
Total power consumption of a cell: more than 50% saving
Average power consumption of a cell: robust to cell size
Z. Wang, W. Zhang, “The Capability of A Separation Architecture for Achieving Energy-efficient Cellular Networking“, IEEE TWC, 2013 (accepted)
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• Separation is not easy!– Challenge 1: difficult to categorize (millions of signal types)
– Challenge 2: Difficult to separate (complicated signal interactions)
– Challenge 3: difficult to manage (synchronization)
Standard Signal TypesCategorize & SeparateCategorize & Separate
Signal Types
Standard
State
FunctionalityFunctionality Separation?
How to Separate? - Principle
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X. Xu, G. He, S. Zhang, Y. Chen and S. Xu, “On Functionality Separation for Future Green Mobile Network: Concept Study over LTE”, IEEE ComMag, May 2013
How to Separate? – State Definition
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How to Separate? - State–Functionality Mapping
State UE Activities
Network Functionalities
Syn.Broadcast of
System Information
Paging Multicast Unicast
Detached Cell Selection √ √
Idle
Acquisition and Update of System Configuration
√ √
Monitoring of Upcoming Transmission Notification
√
Cell Reselection √ √Receiving of MBMS √
Active
Acquisition and Update of System Configuration.
√ √
Monitoring of Upcoming Transmission Notification
√
Cell Handover √ √ √Receiving of MBMS √
Transmission of UE-Specific Data
√
How to Separate? - Functionality–Signal Mapping
Network
Functionality
Signal Types
Syn. PilotFrame
Control
System
Info.
Bearer
Paging
Info.
Bearer
Multicast
Info.
Bearer
Unicast
Info.
Bearer
Syn. √ △
Broadcast
of System
Information
√ △ √
Paging √ √ √
Multicast √ √ √
Unicast √ √ √
△ means this relationship may change among different standards. For example, in GSM/UMTS system, the location of system information bearer is pre-defined and the frame control signal is omitted. However, in LTE systems, the location of system information bearer will be dynamic and the frame control signal is mandatory.
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How to Separate? - Mapping to 3GPP Standard
Signal Types3GPP Standard
GSM UMTS LTE
SynchronizationFCCHSCH
SCH PSS/SSS
Pilot TSCCPICHDPCCH
S-CCPCHRS
Frame ControlAGCHSACCH
PICHMICHAICH
DPCCHS-CCPCH
PHICHPCFICHPDCCHPMCH
Paging Inform. Bearer
PCH S-CCPCH PDSCH
System Inform. Bearer
BCCHSACCH
P-CCPCHPBCH
PDSCH
Multicast Inform. Bearer
CBCH S-CCPCH PMCH
Unicast Inform. Bearer
SDCCHSACCHFACCH
TCH
S-CCPCHDPDCH
PDSCH
A Lab Demo using USRP and OpenBTS
T. Zhao, P. Yang, H. Pan, R. Deng, S. Zhou, and Z. Niu, “Software Defined Radio Implementation of Signaling Splitting in Hyper-Cellular Network,” ACM SIGCOMM Workshop of Software Radio Implementation Forum (SRIF 2013), Hong Kong, Aug. 2013.
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How densely should D-BSs be deployed?
• Problem: For given QoS, how densely should the DBs be deployed for a given coverage and QoS guarantee? – BS density should adapt to traffic dynamics (e.g., cell zooming, BS sleeping)– Deploying more smaller BSs may save energy ?!(increasing sleeping
opportunity)
[1] Z. Niu, Y. Wu, J. Gong, Z. Yang, “Cell zooming for Green cellular networks”, IEEE Com Mag, Nov. 2010 [2] X. Weng, D. Cao, Z. Niu, “Energy-Efficient Cellular Network Planning under Insufficient Cell Zooming”, IEEE VTC2011-spring, Budapest, Hungary, May 2011
0 1 2 3 4 5 60
1
2
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1
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4x 10
-4
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0.05
0.1
0.15
0.2
0.25
到率
Temporal Dynamics Spatial Dynamics Insufficient Zooming Sufficient Zooming
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Optimal BS Density and Tx Power(Homogeneous Case)
Table: Optimal BS density with transmit power adaption (EARTH model)
Conclusion: Joint BS density adjustment and transmit power adaption can help to save more energy!
1. D. Cao, S. Zhou, Z. Niu, “Optimal Combination of Base Station Densities for Cost-Efficient Two-tier Heterogeneous Cellular Networks”, IEEE TWC, Sep. 2013
2. D. Cao, S. Zhou, Z. Niu, “Improving the Energy Efficiency of Two-Tier Heterogeneous Cellular Networks through Partial Spectrum Reuse”, IEEE TWC, Aug. 2013
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Optimal BS Density and Tx Power(Heterogeneous Case)
1. Two‐tier PPP models with BS density ρM and ρm
2. Always connect to the BS with highest SNR (not necessarily the nearest)
Weighted Poisson‐Voronoi Tessellation:
f(A) follows Gamma distribution with density
where:Stochastic Geometry Modeling
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
100
X coordinate
Y c
oord
inat
e
where {CM , Cm} are deployment (energy) cost
Coverageguarantee
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Optimal BS Density and Tx Power(Heterogeneous Case)
• Dynamic BS Sleeping in Dense Urban Scenario (EARTH Model)
– CM = 780 + 28.2PM , Cm = 112 + 5.2Pm
– PM = 20W, Pm =2.42W = 0.0927 < c-1=0.3162
– Reference model: macro-only homogeneous network with no BS sleeping: total energy consumption=3.26 KW/Km2
0.82 (average)(75% saving)
Conclusion: Joint optimization of Macro/Micro‐BS densities can help to save more energy!
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Optimal BS Density – Optimal Policy(Heterogeneous Case)
;
If <c=0.3162, preferentially add micro BSs or sleep macro BSsIf >c=0.3162, preferentially add macro BSs or sleep micro BSs
Ratio of Micro‐BS density and Macro‐BS density ()
Total Energy Density
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Heterogeneous Networks with PSR
• PSR (Partial Spectrum Reuse) to reduce over-provisioningand potential interference (to macro BSs and among micro BSs)
Total Spectrum
Macro BS
Micro BS1
Micro BS2
Micro BS3
D. Cao, S. Zhou, Z. Niu, “Improving the Energy Efficiency of Two-Tier HetwrogeneousCellular Networks through Partial Spectrum Reuse”, to appear at IEEE TWC, Aug. 2013
Optimal β=Wm/WM?
If β<1, allocate FULL spectrum to macro BSs and PARTIAL spectrum to micro BSs; If β>1, vice versa.
2
; ( )m M
M m
C Pe c
C P
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Energy Saving Gain by PSR
PSR achieves the near-optimal performance
PSR can save up to 50% of energy consumption
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How long should a BS sleep?
• Energy-Delay Tradeoff (EDT) in BS Sleeping Control– Longer sleep can save energy, but bring delays to customers
• Wake-up Policies– N-Policy: wake up whenever N new requests come during sleep
– SV-Policy: wake up after a random sleep and then keep awake
– MV-Policy: wake up after a random sleep and sleep again if find no requests
• Challenge #1: Both energy and delay concepts need to be extended– Energy = transmitting power + circuit (processing) power + basic power
– Delay = transmitting delay + queueing delay + sleeping period
• Challenge #2: EDT should be evaluated in the whole network wide– EDT on link-level single-cell level multi-cell level
1. Z. Niu, Jianan Zhang, Xueying Guo, Sheng Zhou, “On the Energy-Delay Tradeoff in Base State Sleep Mode Operation”, IEEE ICCS2012, Singapore, 21-23 Nov., 2012 (invited)
2. X. Guo, S. Zhou, P. R. Kumar, Z. Niu, “Optimal Wake-up Mechanism for Single Base Station with Sleep Mode”, 25th International Teletraffic Congress (ITC25), Shanghai, China, Sep. 2013. (Best Paper Award)
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How long should a BS sleep?
‐ Small delay can help to save energy if well designed‐ N* is related to the switching cost in a square root form‐ Sleeping Control should be used with power adaptation
J. Wu, Z. Niu, S. Zhou, "Traffic-Aware Base Station Sleeping Control and Power Matching for Energy-Delay Tradeoffs in Green Cellular Networks“, IEEE TWC, Vol.12, no.8, Aug. 2013
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Summary
• What’s 5G?– 5G should be a paradigm shift of cellular architecture for Green and Smart
• Major approaches towards 5G – Reduce Energy Waste by Adapting to Real-traffic Dynamics (REWARD)– Traffic-Aware Network Planning and Green Operation (TANGO)– Collaborative and Harmonized Open Radio Ubiquitous Systems (CHORUS)
• A novel Hyper Cellular architecture for 5G– Decoupling signaling functions from data services to make cellular more
adaptive and intelligent– Always-on hyper cells for coverage guarantee and on-demand data cells
• Enabling technologies for 5G– Separation of control and data coverage – Resource/network virtualization and network dimensioning– Traffic adaptation technologies, including cell zooming, BS sleeping,
coverage extension, ……– Energy-delay tradeoff can help to shift the peak and therefore save energy 46
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Concluding Remark
• from World-Wide-Web to World-Wide-Wireless
• for World-Wide-Watch & World-Wide-Wisdom
but definitely should not World-Wide-Wait
and World-Wide-Waste!
: Smart IT for Low-carbon Environment
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For more information, visit http://network.ee.tsinghua.edu.cn/niulab/?category_name=publications