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Future Wireless Broadband Networks: Challenges and Possibilities
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE C802.16-09/0019
Date Submitted:
2009-11-15
Source:
Shilpa Talwar, Kerstin Johnsson, Nageen Himayat, E-mail: {shilpa.talwar, kerstin.johnsson, nageen.himayat}@intel.com
Jose Puthenkulam, Geng Wu, Caroline Chan, Feng Xue, Minnie Ho, Rath Vannithamby, Ozgur Oyman, Wendy Wong, Qinghua Li,
Guangjie Li, Sumeet Sandhu, Sassan Ahmadi, Hujun Yin, Yang-seok Choi
Intel Corporation
Venue:
Atlanta, GA, USA
Base Contribution:
None
Purpose:
For discussion in the Project Planning Adhoc
Notice:
This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed
in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw
material contained herein.
Release:
The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of
an IEEE Standards publication; to copyright in the IEEE‟s name any IEEE Standards publication even though it may include portions of this contribution; and at the
IEEE‟s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that
this contribution may be made public by IEEE 802.16.
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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>.
Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.
Future Wireless Broadband Networks
Challenges and Possibilities
2/1/2010 2
Agenda
• Motivation
• Promising Technologies
• Recommendations
2/1/2010 3
Motivation
2/1/2010 4
Mobile Performance Today
Technology Required Standards Peak Throughput Avg. Spectral Sleep to
Spectrum Completion (Mbps) Efficiency Active
(Expected) (bits/sec/Hz/Sector) Latency
DL UL DL UL
802.16e/Mobile 10 MHz Dec. 2005 40 17 1.4 0.7 < 40 ms
WiMAX Release 1.0 (5:3)
2x2 MIMO TDD
HSPA (Release 6) 2x5 MHz Mar. 2005 14 6 0.5 0.3 250 ms
FDD
HSPA+ (Release 8) 2x5 MHz Dec. 2008 42 12 0.8 0.5 50 ms
2x2 MIMO FDD
LTE (Release 8) 2x10 MHz Mar. 2009 86 38 1.6 0.8 10 ms
2x2 MIMO FDD
LTE (Release 10) 2x10 MHz (Q1 2011) 160 80 2.4 2.1 <10ms
4x4 MIMO FDD
802.16m 20 MHz (Q3, 2010) 170 90 2.9 2.5 <10 ms
4x4 MIMO TDD (5:3)
All peak throughput numbers (except for WiMAX 1.0) exclude the impact of control & coding overhead
3GPP data rate numbers are from 3GPP document TR 25.912, page 55 and average of NGMN documents for LTE
3GPP Latency numbers are from 3GPP 25.999 & 3GPP 36.912
3GPP LTE Release 10 numbers are from the 3GPP ITU-R IMT-Advanced submission TR 36.912 with L=3 for pragmatic overhead calculation
WiMAX Release 1.0 uplink assumes virtual MIMO
802.16e/WiMAX 1.0 spectral efficiency numbers are based on NGMN evaluation methodology
802.16m is based on ITU-R IMT-Advanced submission evaluation and for urban macro –cell
802.16m leads in performance. In performance availability, 802.16e leads
2/1/2010 5
Commercial Broadband Standards
LANs Wireless LANs Wireless MANs
IEEE 802.3 Standards* IEEE 802.11 Standards* IEEE 802.16 Standards*
802.11b (2.4 GHz)
802.11g (2.4 GHz) 802.16e (Licensed <6 GHz)
802.11a (5 GHz) P802.16m (Licensed <6 GHz)
802.11n (2.4, 5 GHz) (under development)
+ + +
+
+
Current Peak: 10Gbps Current Peak: 600Mbps Current Peak: 300Mbps
Target Peak Target Peak Target Peak
IEEE P802.3ba : 40/100 Gbps IEEE P802.11ac (5GHz): >1 Gbps
IEEE P802.11ad (60GHz):>1-3 Gbps >1 Gbps?
Peak Rates of >1 Gbps potential target for Wireless Broadband
+Logos and trademarks belong to the other entities *Not a complete list of IEEE 802 standards
2/1/2010 6
What is happening in Marketplace?
• Broadband traffic is growing
exponentially with introduction of new
devices: iPhones and Netbooks
• Larger screen mobile devices drive up
data usage: eg. iPhone consumes 30x
data
Morgan Stanley, Economy + Internet Trends, Oct 2009 iPhone Netbook
Morgan Stanley
2/1/2010 7
Fixed to Mobile Transition is happening
– Consumers prefer wireless devices over wired
– Voice: Users moving from landline to mobile for cost & convenience (ex. Finland has
60% mobile-only households)
– Internet: “Mobile internet adoption has outpaced desktop” (Morgan Stanley)
2/1/2010 8
Opportunity to connect more Devices
Boost number of mobile subscribers and devices connected to Internet (e.g. 700M now
in China, 450M in India)
“In the longer term, small wireless sensor devices embedded in objects, equipment and
facilities are likely to be integrated with the Internet through wireless networks that
will enable interconnectivity anywhere and at anytime”
- OECD Policy Brief, June 2008
2/1/2010 9
Challenge – Very High Capacity
Wireless network data usage demand expected to grow by 5x – 20x in next 5-10
years
X
Increasing device density Increasing device data rates
Spectral Efficiency gains typically limited to 2-3x every generation of Air Interface
Growth in bandwidth demand is accelerating need for Innovations at all levels
2/1/2010 10
Challenge – Lower Revenue per bit
• Service providers are facing challenges at both ends
– Invest in network capacity to meet demand
– Increase revenue with new applications and services
• Cost of Network deployments to meet demand is increasing faster than revenue
Future networks need to drastically lower Cost per Bit, and enable new Services
2/1/2010 11
Service provider options – the big picture
Rationalize
Invest in Capacity Create New Revenue
Network Usage
• Tiered service levels • Buy more spectrum • Exclusive devices
• Traffic shaping • Split Cells • Enterprise Services
• Deploy new • Applications Store
technologies
• M2M – new business
• Deploy multi-tier
networks
• Exploit multiple
protocols
Focus of this Presentation is on Technologies with Standards implications
2/1/2010 12
Investing in Capacity
Technique Status/Issues Possibilities
Deploy more spectrum Low frequency spectrum is limited & Target higher frequencies: 3.6-4.9
expensive GHz (802.16), 60GHz (802.11)
Synergistic use with unlicensed
bands (802.11 & 802.16)
Reuse Spectrum Simple cell splitting, Relays, Pico, Smart Multi-tier Networks reusing
Micro, Femto same spectrum
Limited by infrastructure Cost Interference Management
Link capacity Theoretical link capacity nearly Higher order MIMO
achieved (Shannon)
MIMO (4x4) capacity in 802 .11n/16m
Cell capacity Significant gains harnessed in Higher order MU-MIMO
802.16m: MU-MIMO, MAC
enhancements Client co-operation
Multi-cell/Network Simple techniques included in 16m: Network MIMO
Capacity FFR, uplink multi-cell Power Control,
Coordinated BF Interference Alignment
Expect next set of disruptive gains to
come from multi-cell topologies &
techniques
2/1/2010 13
Creating new services
M2M: automated flow of data from machine to machine
• Opportunity to boost revenues from $20 billion in 2006 to more than $220 billion by 2010 (Gartner)
• M2M enables large set of applications
Technique Status/Issues Possibilities
Machine-to-Machine Networks today can meet needs of Optimize air interface for M2M
Connectivity high-end applications
• Ultra-Low power
Low end applications need cost-
effective solutions • Low cost
• Scalability across apps
2/1/2010 14
Promising Technologies
2/1/2010 15
Potential Coverage & Capacity Gains
Spectral Efficiency
Indoor Energy (Macro)
Technique Peak Rate
Coverage Efficiency
Avg. Cell-edge
Carrier Aggregation Primary
Spectrum
Multi-tier Networks* Primary Secondary Secondary
Utilization
Unlicensed use (WiFi)* Primary Secondary Primary Secondary
Link
Higher order MIMO Primary Secondary Secondary
Capacity
Higher order MU-MIMO Primary Primary
Cell
Capacity
Client Co-operation Secondary Primary Secondary Primary
Network MIMO Primary Primary Primary
Network
Capacity
Interference Alignment Primary Primary
*Not an exhaustive list…
2/1/2010 16
Spectrum Utilization
Multi-tier Networks
Idea
• Overlay multiple tiers of cells, macro/pico/femto, potentially sharing common
spectrum
• Client-to-client communication can be viewed as an additional tier (see client co-
operation)
• Tiers can be heterogeneous (802.16 and 802.11)
Femto/WiFi-AP
(Offload Macro-BS)
Macro-BS
Femto-AP Pico-BS
(Indoor coverage & offload macro-BS) (Areal capacity)
Client Relay
Wireless Access
Relay Wireless backhaul
Coverage Hole
2/1/2010 17
Spectrum Utilization
Advantages of Multi-tier
Networks
• Significant gains in areal capacity via
aggressive spectrum reuse and use of
unlicensed bands
– E.g.: Co-channel femto-cells provide linear
gains in areal capacity with increasing number
of femto-AP’s in a multi-tier deployment
• Cost structure of smaller cells (pico and
femto) is more favorable
• Indoor coverage is improved through low
cost femto-cells
Source: Johansson at al, „A Methodology for Estimating Cost and Performance of
Heterogeneous Wireless Access Networks‟, PIMRC‟07.
Significant potential savings in cost per bit via multi-tier networks
2/1/2010 18
Spectrum Utilization
Challenges with Multi-tier Networks
• Cross-tier interference
• Tiers cause significant interference to each other; problem worse with closed
BSs
• E.g. Macro/Femto deployment
– Closed femto-cell transmissions cause significant interference to macro-users
– Interference to data can be addressed with intelligent use of FFR partitions
and/or FFZ
– Interference to control can not be addressed using FFR or FFZ
Max FAP FAP-free Outdoor Indoor 50% Outdoor 50% Indoor
Tx Scheme
Tx Pwr zones Outage (%) Outage (%) rate (Mbps) rate (Mbps)
FFR only 3.0 17.0 0.07 0.03
0dBm No FFZ 40.2 0.9 0.02 16.3
FFR + Femto-Tx on FFZ 3.0 0.5 0.06 11.3
all FFR partitions
10dBm No FFZ 76.2 0.4 0.00 21.4
FFZ 3.0 0.3 0.08 7.95
• Mobility management
• At moderate to high speed, handovers across small cells costly
• Need intelligent schemes to determine conditions for handover intra- and
inter-tiers
•
2/1/2010 SON 19
Spectrum Utilization
Heterogeneous Networks
Idea
• Exploit multiple radio interfaces co-located at the network
– WiFi/WiMAX interfaces in operator controlled femto-cell networks
• Utilize licensed and unlicensed spectrum
– Virtual WiMAX carrier available through WiFi
– Multi-network access possible for single-radio client
Integrated WiFi/ WiMax
Integrated WiFi/ WiMax
Femtocell MyFi
MyFi
WAN
Multi radio device
Multi - radio device
Femtocell WiMAX
WiMAX
WiFi WiFi
WiMAX/WiFi Mobile
WiMAX/WiFi Mobile WiFi
Internet Device
Internet Device
Simultaneous
Virtual Carrier (WiFi)
Multi - radio Operation Mobile Hotspot
Mobile Hotspot
2/1/2010 20
Spectrum Utilization
Heterogeneous Networks
Deployment Scenarios
Hotspot
Multi-radio
Smart-Phone
Home
Integrated
Femto-AP
Integrated
Pico-cell
Enterprise Mobile Hotspot
Laptop w/
WiFi & WiMAX
Multi-radio
Device
Integrated
Femto-AP
2/1/2010 21
Spectrum Utilization
Heterogeneous Network Techniques
Idea Enhanced Spectrum Description Target Gains
Utilization Techniques
Virtual Interference Dynamically switch between Increases system
WiMAX Avoidance WiFi & WiMAX to avoid throughput ~3x
carrier interference
Diversity/Redundancy Use added spectrum to improve Increases SINR ~3-5 dB,
Transmission diversity, code rates with decreases cell-edge outage
incremental redundancy
Carrier Aggregation Use added spectrum to transmit Increases peak throughput
independent data streams ~2-3x
QoS/ Load Balancing QoS-aware mapping of apps to Improves QoS, system
different spectrum capacity
Multi- Routing/Access Provide connectivity between Improves connectivity,
network heterogeneous protocols coverage
access
2/1/2010 22
Spectrum Utilization
Heterogeneous Network Challenges
Network (AP/BS) Multi-Radio protocols required
MRRM • Define Generic Link Layer (GLL) *
• Manage interworking between heterogeneous links
• Define Multi-Radio Resource Management (MRRM) *
GLL
WLAN WiMAX OTHER • Manage radio resources across heterogeneous links
Example: Spectrum aggregation
WLAN WiMAX OTHER
GLL • Available in WiMAX & WiFi currently
• WiFi channel bonding at PHY layer w/ MAC coordination
• WiMAX carrier aggregation at MAC layer
MRRM
• Protocols required to combine WiFi & WiMAX carriers
Multi-Radio Client
* WINNER Definition
Develop integrated multi-radio protocol design for 802.16/11
2/1/2010 23
Cell Capacity
Client Co-operation
Poor WWAN link
MID with WWAN & WLAN
Good WWAN link
Good WLAN link
WWAN BS
Laptop with WWAN & WLAN
Client Cooperation is a technique where clients interact to jointly transmit and/or receive information
in wireless environments.
Idea: Exploit client clustering and P2P communication to transmit/receive information over multiple
paths between BS and client.
Benefit: Performance improvement in throughput, capacity and reliability without increased
infrastructure cost.
Usage: Clusters of stationary/nomadic clients with WLAN P2P connectivity that share WWAN service
provider
2/1/2010 24
Cell Capacity
Client Cooperation Gains
2.6
Uncorrelated WiMAX channels
Correlated WiMAX channels
2.4
With 7 neighbors:
220% gain w/ uncorr
2.2
Average spectral efficiency (bps/Hz)
2
1.8
With 5 neighbors:
35% gain w/ corr
195% gain w/ uncorr
1.6
With 3 neighbors:
27% gain w/ corr
150% gain w/ uncorr
1.4
With 1 neighbor:
1.2 12% gain w/ corr
86% gain w/ uncorr
1
0.8
No cooperation
1 2 3 4 5 6 7 8
Cluster size
2/1/2010 25
Cell Capacity
Client Cooperation enabled via 802.16/11
WiMAX frame
DL subframe index UL subframe index
0 1 2 3 4 0 1 2
BS
MAP + DL Data Burst
(MS & Coop check for allocations given to
their Coop STID and listen for bursts)
MS
WiFi: HARQ + UL Data Burst
Coop tx rec’d DL burst to MS. MS tx UL (MS tx burst)
burst to Coop.
Cooperator
UL Data Burst
(If Coop successfully rec‟d burst from
MS, it tx it at same time)
2/1/2010 26
Cell Capacity
Client Cooperation Issues
• Power
– Reduces power consumed by WiMAX transmissions
• Client Cooperation reduces re-transmissions and boosts MCS per
burst
– Power consumed by WiFi transmissions is TBD
• Power is consumed when MS and cooperator exchange packets;
increases with probability of WiFi collisions
• Power also consumed by neighbor discovery and cooperator
selection protocols
• Security
– Control and data packets are protected
– Sharing MS STID with cooperator may facilitate denial of service
attacks
• Accounting
– Not required, but enabling accounting enlarges market
2/1/2010 27
Cell Capacity
Client Cooperation Standards Impacts
• 802.11/WiFi
– Peer-to-peer WiFi connectivity required
– Neighbor Discovery and Cooperator Selection protocols need to
be enabled in P2P WiFi mode
• 802.16/WiMAX
– Enable coordinated Neighbor Discovery opportunities
• Speeds up WiFi Neighbor Discovery – saves power
• Increases probability of discovery – improves cooperator selection
– Provide shared cooperator/MS STID
• Establishes cooperative relationship without sharing MS STID
• Allows central entity to do accounting
2/1/2010 28
Network Capacity
Network MIMO
Idea
• Network MIMO algorithms enabled by central cloud processing
• Cooperative MIMO, Distributed Antennas
Converged wireless Cloud
Processing server
Fiber
DAS with 4 distributed antennas show
nearly 300% gain over CAS by utilizing
Distributed Antennas MU MIMO protocol in system evaluation
2/1/2010 29
Network Capacity
Interference Alignment
Tx signal Rx signal
Idea
• Align transmit directions so that interfering
signals all come from the same “direction”
(subspace)
• Alignment can be across antennas, frequency,
time
• Benefits: Improves uplink and downlink
transmissions of cell-edge users;
Low receiver complexity
• Challenge: Practical schemes that can achieve
theoretical gain
Performance (theory) in high SNR regime: If there are K
pairs and each node has M antennas, then KM/2 degrees
of freedom are achievable. For comparison, perfect
resource sharing achieves 1 degree of freedom.
(Cadambe & Jafar 2008)
2/1/2010 30
Recommendations
• New System/technology needed to drive
increased capacity
• New Radio network topologies needed for lower
cost per bit
• Plan for next generation 802.16 standard
needed
2/1/2010 31
