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.
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Future Wireless Broadband Networks
Challenges and Possibilities
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Agenda
• Motivation
• Promising Technologies
• Recommendations
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Motivation
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Mobile Performance Today
Technology
Required
Spectrum
Standards
Completion
(Expected)
Peak Throughput
(Mbps)
DL
UL
Avg. Spectral
Efficiency
(bits/sec/Hz/Sector)
DL
Sleep to
Active
Latency
UL
802.16e/Mobile
WiMAX Release 1.0
2x2 MIMO TDD
10 MHz
(5:3)
Dec. 2005
40
17
1.4
0.7
< 40 ms
HSPA (Release 6)
FDD
2x5 MHz
Mar. 2005
14
6
0.5
0.3
250 ms
HSPA+ (Release 8)
2x2 MIMO FDD
2x5 MHz
Dec. 2008
42
12
0.8
0.5
50 ms
LTE (Release 8)
2x2 MIMO FDD
2x10 MHz
Mar. 2009
86
38
1.6
0.8
10 ms
LTE (Release 10)
4x4 MIMO FDD
2x10 MHz
(Q1 2011)
160
80
2.4
2.1
<10ms
802.16m
4x4 MIMO TDD
20 MHz
(5:3)
(Q3, 2010)
170
90
2.9
2.5
<10 ms
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
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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)
802.11a (5 GHz)
802.11n (2.4, 5 GHz)
802.16e (Licensed <6 GHz)
P802.16m (Licensed <6 GHz)
(under development)
+
+
+
+
+
Current Peak: 10Gbps
Current Peak: 600Mbps
Current Peak: 300Mbps
Target Peak
IEEE P802.3ba : 40/100 Gbps
Target Peak
IEEE P802.11ac (5GHz): >1 Gbps
IEEE P802.11ad (60GHz):>1-3 Gbps
Target Peak
>1 Gbps?
Peak Rates of >1 Gbps potential target for Wireless Broadband
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+Logos and trademarks belong to the other entities
*Not a complete list of IEEE 802 standards
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
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Fixed to Mobile Transition is happening
–
–
–
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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)
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
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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
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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
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Service provider options – the big picture
Rationalize
Network Usage
Invest in Capacity
Create New Revenue
• Tiered service levels
• Buy more spectrum
• Exclusive devices
• Traffic shaping
• Split Cells
• Enterprise Services
• Deploy new
technologies
• Applications Store
• Deploy multi-tier
networks
• M2M – new business
• Exploit multiple
protocols
Focus of this Presentation is on Technologies with Standards implications
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Investing in Capacity
Technique
Deploy more spectrum
Status/Issues
Low frequency spectrum is limited &
expensive
Possibilities
Target higher frequencies: 3.6-4.9
GHz (802.16), 60GHz (802.11)
Synergistic use with unlicensed
bands (802.11 & 802.16)
Reuse Spectrum
Link capacity
Simple cell splitting, Relays, Pico,
Micro, Femto
Smart Multi-tier Networks reusing
same spectrum
Limited by infrastructure Cost
Interference Management
Theoretical link capacity nearly
achieved (Shannon)
Higher order MIMO
MIMO (4x4) capacity in 802 .11n/16m
Cell capacity
Multi-cell/Network
Capacity
Significant gains harnessed in
802.16m: MU-MIMO, MAC
enhancements
Higher order MU-MIMO
Simple techniques included in 16m:
FFR, uplink multi-cell Power Control,
Coordinated BF
Network MIMO
Client co-operation
Interference Alignment
Expect next set of disruptive gains to
come from multi-cell topologies &
techniques
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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
Machine-to-Machine
Connectivity
Status/Issues
Networks today can meet needs of
high-end applications
Low end applications need costeffective solutions
Possibilities
Optimize air interface for M2M
• Ultra-Low power
• Low cost
• Scalability across apps
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Promising Technologies
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Potential Coverage & Capacity Gains
Technique
Indoor
Coverage
Energy
Efficiency
Carrier Aggregation
Spectrum
Utilization
Link
Capacity
Cell
Capacity
Network
Capacity
Primary
Secondary
Unlicensed use (WiFi)*
Primary
Secondary
Higher order MIMO
Interference Alignment
Cell-edge
Secondary
Primary
Primary
Secondary
Secondary
Secondary
Secondary
Primary
Primary
Primary
Secondary
Primary
Primary
Primary
Primary
Primary
Primary
Higher order MU-MIMO
Network MIMO
Avg.
Primary
Multi-tier Networks*
Client Co-operation
Peak Rate
Spectral Efficiency
(Macro)
*Not an exhaustive list…
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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
(Indoor coverage & offload macro-BS)
Pico-BS
(Areal capacity)
Client Relay
Wireless Access
Relay
Wireless backhaul
Coverage Hole
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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 femtoAP’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
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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
Tx Scheme
Max FAP
Tx Pwr
FAP-free
zones
Outdoor
Outage (%)
Indoor
Outage (%)
50% Outdoor
rate (Mbps)
50% Indoor
rate (Mbps)
3.0
17.0
0.07
0.03
No FFZ
40.2
0.9
0.02
16.3
FFZ
3.0
0.5
0.06
11.3
No FFZ
76.2
0.4
0.00
21.4
FFZ
3.0
0.3
0.08
7.95
FFR only
0dBm
FFR + Femto-Tx on
all FFR partitions
•
10dBm
Mobility management
• At moderate to high speed, handovers across small cells costly
• Need intelligent schemes to determine conditions for handover intra- and inter-tiers
•
SON
• Need self organization/management across tiers to lower OPEX
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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
Femtocell
MyFi
MyFi
Multi - radio
radio device
device
Multi
WAN
WiMAX
WiMAX
WiFi
WiFi
WiMAX/WiFi Mobile
WiMAX/WiFi
Mobile
Internet Device
WiFi
Internet Device
Simultaneous
Virtual
Carrier
(WiFi)
Multi - radio
Operation
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Mobile
MobileHotspot
Hotspot
20
Spectrum Utilization
Heterogeneous Networks
Deployment Scenarios
Home
Multi-radio
Smart-Phone
Hotspot
Integrated
Femto-AP
Integrated
Pico-cell
Enterprise
Mobile Hotspot
Laptop w/
WiFi & WiMAX
Multi-radio
Device
Integrated
Femto-AP
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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
QoS/ Load Balancing
Multinetwork
Routing/Access
Use added spectrum to transmit
Increases peak throughput
independent data streams
~2-3x
QoS-aware mapping of apps to
Improves QoS, system
different spectrum
capacity
Provide connectivity between
Improves connectivity,
heterogeneous protocols
coverage
access
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Spectrum Utilization
Heterogeneous Network Challenges
Network (AP/BS)
MRRM
Multi-Radio protocols required
• Define Generic Link Layer (GLL) *
• Manage interworking between heterogeneous links
GLL
WLAN WiMAX OTHER
• Define Multi-Radio Resource Management (MRRM) *
• 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
Multi-Radio Client
• Protocols required to combine WiFi & WiMAX carriers
* WINNER Definition
Develop integrated multi-radio protocol design for 802.16/11
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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
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Cell Capacity
Client Cooperation Gains
2.6
Uncorrelated WiMAX channels
Correlated WiMAX channels
2.4
Average spectral efficiency (bps/Hz)
With 7 neighbors:
220% gain w/ uncorr
2.2
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:
12% gain w/ corr
86% gain w/ uncorr
1.2
1
0.8
No cooperation
1
2
3
4
5
6
7
8
Cluster size
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Cell Capacity
Client Cooperation enabled via 802.16/11
WiMAX frame
DL subframe index
0
1
UL subframe index
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:
Coop tx rec’d DL burst to MS. MS tx UL
burst to Coop.
HARQ + UL Data Burst
(MS tx burst)
Cooperator
UL Data Burst
(If Coop successfully rec’d burst from
MS, it tx it at same time)
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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
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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
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Network Capacity
Network MIMO
Idea
•
•
Network MIMO algorithms enabled by central cloud processing
Cooperative MIMO, Distributed Antennas
Converged wireless Cloud
Processing server
Fiber
Distributed Antennas
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DAS with 4 distributed antennas show
nearly 300% gain over CAS by utilizing
MU MIMO protocol in system evaluation
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Network Capacity
Interference Alignment
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;
Tx signal
Rx signal
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)
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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
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