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San Diego

Wireless Communications Networks – Research Challenges and Opportunities

John E. Smee, Ph.D.

Director, Engineering

Qualcomm Research

NITRD Workshop

Washington, DC

9/20/12

Data Traffic Growth

10–12x Mobile data traffic projected to grow

from 2010–2015

1000x Potentially up to

from 2010–2020

New Techniques Network Offload More Spectrum Het Nets

Reshaping Industries

Another Wave of Wireless Growth Coming

Health Care Energy

Auto Banking/Finance

Media/ Entertainment

Advertising

Computing

Retail

Mobile Video is Expected to Grow Dramatically

in Next 5 Years

• Mobile video spending is

expected to reach ~$14B

by 2016

• 70% of all mobile traffic

will consist of mobile

video by 2016

Source: Strategy Analytics, March 2011

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

2011 2012 2013 2014 2015 2016

Global Mobile Video Spending Forecast ($Billions)

Advertising Spend

Transport and PremiumSpend

Wireless Network Challenges / Opportunities

• Growing need to optimize network capacity while

1. Attaining robust mobility

2. Supporting planned and ad-hoc deployments

3. Enhancing user experience and fairness

4. Leveraging licensed (e.g. 3G/LTE and unlicensed (WLAN) networks

5. Dealing with backhaul variability, interference dynamics in co-channel and adjacent channel deployments

6. Minimizing power consumption

7. Solving multi-radio coexistence/interference issues

Dimensions of Wireless Network Improvements

Leverage wider bandwidth Carrier aggregation across

multiple carriers and multiple bands

Leverage heterogeneous network topology (HetNet)

With advanced interference management (low power picocells with adaptive resource partitioning

and advanced receiver based devices)

Leverage more radio links, more antennas

Downlink MIMO up to 8x8, enhanced Multi User MIMO and uplink MIMO up to 4x4

Primarily higher data rates

(bps)

Higher spectral efficiency

(bps/Hz)

Higher spectral efficiency per coverage area

(bps/Hz/km2)

The Next Leap In Performance—Small Cells

Adding small cells like

Picocells, Femtocells,

and Remote

Radioheads

How do we get more capacity?

Bring Network Closer to Users—Small Cells

Optimizations Makes the Leap Even Bigger—Smart HetNets

Radio Link approaching theoretical limit

Better Techniques Such as higher order MIMO, Smart Networks

More Spectrum New bands, Re-farming Aggregate TDD spectrum

8

Dense Het Nets – heading to “1 user per “cell”

with Macros, Picos, Relays, and many Femtos

Wireless Networking Research

• Challenge

– Supporting huge traffic growth with economically viable deployments

• Perspective on Breakthroughs Needed

– Improvements in deployment, devices, networks

– Mix of planned and ad-hoc

– Robust and adaptive approaches

• Turning Research into Societal Impact

– Focus on extensibility and viability of solution

– Real world data coupled with analysis and simulation

– Pace of innovation in wireless industry device capabilities and wireless standards is very high -- Evaluate research in context of current standards and brand new models

• Appendix slides with examples of some

wireless network research areas

LTE-Advanced: Further Enhancement of LTE

Range Extension,

Resource Partitioning To Enable Plug-n-Play, Advanced

UE Receivers • Plug-n-Play Relays

• Picos & Femtos

• Remote Radioheads

• Self Organizing Networks

• Range Extension

• Resource Partitioning To Enable Plug-n-Play

• Advanced UE Receivers

• Wider bandwidth

• Higher peak rates

• Efficient use of fragmented spectrum

• Asymmetric UL/DL bandwidth

• eNBs collaborating to enhance performance through multi-antenna gains and interference reduction

HETEROGENEOUS NETWORKS

INTERFERENCE MANAGEMENT

CARRIER AGGREGATION

COMP MULTIPOINT TRANSMISSION

12

WiFi Advanced—Next Generation WLAN

5 GHz Band (802.11ac)

• Evolution of 11n WLAN, > 1 Gbps

• MU-MIMO—up to 8 antenna AP 20/40/80/160 MHz bandwidth

• On path to commercialization in multiple MSMs and QC-Atheros APs

900 MHz Band (802.11ah) Sensors, M2M, Internet of Things

600 MHz Band (802.11af) TVWS for Cellular Offloading

Low Cost Access, Hetnets and

WiFi-Direct Enhancements

60 GHz Band (802.11ad) Multi-Gbps Sync-n-Go

SET-TOP BOXES/MEDIA

SERVERS

TV

PICTURE-FRAMES/ OTHER DISPLAYS

CAMCORDERS/ CAMERAS

ONLINE CAMERAS

Multi-radio Revolution

Multiple wireless applications

eMBMS

Entertainment Location

GPS

Connectivity

C2K, UMTS,

LTE

WWAN Voice/Data

Concurrent multi-radio operation is becoming the norm…

on capable devices, and

evolving usage models

Traffic Management-- Connectivity Engine for

Smart Interface Selection

3G/LTE

?

Wi-Fi

Radio Conditions

Policies

Congestion

Latency & Bandwidth

QoS, RSSI, FER

Battery Life etc.

Automatic selection of the best radio based on:

• Operator Policies • Multi Radio Environment • Application Requirements • User Preferences

Seamless offload between 3G/LTE and Wi-Fi

• IP Flow Mobility with DSMIPv6 • Seamless Handovers

Automatic Radio Selection Algorithms

Wi-Fi ACCESS POINT

BASE STATION

Integration of WiFi into 3G/4G Allows

Better Load Balancing

• Standalone WiFi offers opportunistic offloading for mobile traffic

– Combined small cells and WiFi offers best overall coverage, capacity and user

experience

• Control plane interworking will enable the management of WiFi

access via LTE/UMTS

– Allows more dynamic and reliable control of offloading

• User plane interworking will enable WiFi as an additional carrier to be

aggregated with LTE

– Options of bearer-level or packet-level aggregation based on node and

backhaul type

COMBINED PICO/WIFI

TM

WiFi for indoor and hotspot offloading

Adaptive Interference Management Adapts to

Network Changes And Actual Network Load

1Advanced adaptive interference management : enhanced time-domain adaptive resource partitioning with enhanced RRM/RLM and advanced receiver devices

Provides network load balancing

Benefits all Hetnets—but necessary for dense HetNets

Adapts to typically uneven load that changes with time and location

Heavy Load

Medium Load

Light Load

Adapts to added nodes, like Picocells

Hyper-dense Network Using More Spectrum

To Accommodate Future Traffic Growth

More Capacity with 100’s of MHz Spectrum

And Small Cell Densification

WIDE AREA SPECTRUM 700–2600 MHz

For macro and initial small cell deployment

LOCAL AREA SPECTRUM 3–6 GHz

Hotspot Capacity Boost

BRING NETWORK CLOSER TO USER FOR

NEXT LEAP OF PERFORMANCE

18

Interference Channels – Communications/Information Theory challenge to Turn Theory into Practice

Transmission rate control to avoid bursty interference

If not, rate can gravitate to the worst

HetNet Interference Management

• LTE Rel-10/11 eICIC and advanced receivers offer inter-cell

interference management

– Macro and small cells use Almost-Blank Subframe (ABS) for resource partitioning

– Advanced UE receiver suppresses the residual interference in ABS

• Performs cancellation of common signaling: CRS/PSS/SSS/PBCH

Small cell

Cell Range Expansion Enabled by eICIC and advanced receiver

Subframes reserved for Macro

Macro DL

Small Cell DL

Almost Blank Subframes

Time-Domain Resources Subframes reserved for

small cell CRE region Subframes for small cell center region

Time Domain Partitioning Example

Additional Receiver Enhancements

for More Flexibility and Gains

• Further enhancement of UE advanced receiver provides flexibility and capacity gains for eICIC

– Allow control and data transmission in ABS not subjected to eICIC partitioning

– Recover the dimension loss due to ABS subframe partitioning

• Allows Macro to transmit control and data in subframes where small cells serve CRE UEs

– Increase uplink capacity • Decouple eICIC TDM partitioning pattern for UL and DL

Subframes reserved for Macro

Macro DL

Small Cell DL

Almost Blank Subframes (ABS)

Subframes reserved for small cell CRE region

SIB1/Paging and associated control channels (PCFICH & PDCCH) is allowed in ABS

Subframes serving small cell CRE enabled by enhanced receiver

Interference Enhanced

Interference Cancellation

LTE C

arrier #5

LTE C

arrier #4

LTE C

arrier #3

LTE C

arrier #2

LTE C

arrier #1

Aggregated Data Pipe

Carrier Aggregation Leverages All Spectrum Assets

Aggregate spectrum within a band to create a fatter data pipe

Aggregate across spectrum bands

Aggregate more downlink capacity— supplemental downlink (unpaired spectrum)

Enhances heterogeneous networks (multiple carriers)

Aggregation within band E.g. 2.6 GHz

10 MHz

Macro Pico

Carrier 1

Carrier 2

Pico

Example: Carrier 1 used for wide area macro coverage, but also by picocells, carrier 2 used by all nodes, but with lower power around macrocell

10 MHz

Supplemental Downlink E.g. 700MHz

LTE Multi-Flow Enhances Carrier Aggregation(CA)

• Packet-level aggregation using fast backhaul allows choosing serving cell for each IP packet based on scheduling on each cell

• Bearer-level aggregation for non co-located nodes relies on per bearer decision where to serve each IP packet

Improved User Experience

• Extend CA across non co-located nodes

• Agile connection to nodes in enhanced layer

Efficient Load Balancing

• Utilize unused capacity across multiple nodes

• Improved overall system capacity

Mobility

Robustness

• Stable connection to macro base layer

• Reduced signaling load to core network for nomadic UEs

Opportunistic Small Cell Operation For Reduced

Interference And Energy Efficiency

• A small cell can be put into dormant mode when there is no active users nearby

– Reduce common channel interference to neighboring cells and power consumption

– Periodically monitor uplink signals from connected UEs served by macro or neighboring cells

• Transition into active mode when needed so UEs can be attached to the cell

S2 in dormant mode; No DL transmission

Macro S1 S2

S2 detects nearby connected UE

S1 S1 S2 S2

S2 transitions to active mode and

starts to serve UEs

Opportunistic Relays For Backhaul Constraints

Relay Relay

Core Network

– Relay uses existing licensed spectrum for backhaul link

• Backhaul is provided by a LTE link to a macro or pico cell

• Allows flexible site selection regardless of traditional backhaul availability

• Reduce backhaul cost and operating expenses

– Smart utilization of resources allows Relays to offer capacity gains

• Allows for more flexibility to densify network

• Opportunistic operation further reduces interference and power

consumption

A New Network Deployment Model:

Open Access Neighborhood Small Cells (NSC)

25

LOW COST DEPLOYMENT

• Leverages existing sites and backhaul

• Minimal CapEx and OpEx

• Simple plug-n-play

MORE SPECTRUM

• Can use high frequency bands due to smaller coverage area requirement

HIGH CAPACITY

• Huge capacity gains both for indoor and outdoor users

• At high density each small cell serves to one user

Dense Urban Neighborhood Small Cells Simulation Assumptions

Red: 2 story bldg Blue: 3 story bldg

Green: 4 story bldg Cyan: 5 story bldg

Yellow: 6 story bldg

Dense-Urban Area (Simulation with Apartment Buildings)

Black star: Small Cell

Magenta Circle: Mobile

Blue circle: Macrocell

met

er

Notes: a) Small cells are randomly dropped in a apartment statistically

independent of other small cell locations b) At the most one Small Cell is dropped in any apartment

Parameter Value

Macrocell ISD 500m

Population Density 20000 per sq km

Number of Apartments per Macrocell

(2 subs per Apt.) 720

User Distribution

70% Indoors/ 30% Outdoors;

Randomly dropped

Exceeding 1000x Capacity Gain With Dense

Neighborhood Small Cells And More Spectrum

• 500m ISD, 720 apartments/cell, 2 subs/apartment. Users randomly dropped, 70% indoor and 30% outdoor, 2x2 MIMO • Gains relative to baseline with macros only. Macros deployed in 10 MHz bandwidth at 2 GHz. Small cells deployed at 3.5 GHz • Small cell penetration is percentage of total apartments per macrocell (720) with a Small Cell. For a particular operator, this number cannot exceed its own

market share. For example, an operator with 30% market share can at most have 216 small cells in a macro (assuming no small cell is deployed outside customer premise by the operator).

(360 small cells)

0x

200x

400x

600x

800x

1,000x

1,200x

1,400x

1,600x

1,800x

0% 10% 20% 30% 40% 50%

DL

Me

dia

n T

hro

ugh

pu

t G

ain

(x)

Small cell Penetration (%)

DL Median Throughput Gain (LTE, dense urban, 100 MHz small cells in 3.5 GHz, relative to

macros only) 25 UEs/macro 200 UEs/macro

(72 small cells)

1000x capacity at 20% small cell penetration

Qualcomm Confidential and Proprietary — Restricted Distribution - DO NOT COPY

MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION —

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