Wireless-Optical Convergence: The Case for Fibre-connected Massively Distributed Antennas

Prof. Victor C. M. LeungTELUS Mobility Research Chair in Advanced Telecom. Eng.

Department of Electrical and Computer EngineeringThe University of British Columbia

IEEE ComSoc Distinguished Lecture TourJune, 2011 © 2011

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Outline

• Introduction– University of British Columbia

– Dept. of Electrical and Computer Engineering

– My research area and research team

• Architecture of broadband wireless access with fibre-

connected massively distributed antennas (BWA-FMDA)

• BWA-FMDA in license-free band: Cognitive WLAN over

fibres

• BWA-FMDA in licensed band: CoMP of LTE femto-cells

• Conclusions

Introduction

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The University of British Columbia

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The University of British Columbia• 103 years old public university with four-year undergraduate programs

• A world class university with spectacular locations

• Consistently ranked among world’s top 50 universities • #30, London Times Higher Education World University Ranking 2010

• #36, Shanghai Jiaotong University World University Ranking 2010

• Annual budget of over $1,800,000,000

• More than 50,000 students, more than 7500 international students

• 18 faculties and 14 schools, 2 campuses in Vancouver and Kelowna

• World class faculties in medicine, life sciences, law, engineering and management

• Seven Nobel Laureates among current or former faculty and alumni• Michael Smith, Nobel Prize in chemistry, 1993

• Carl Wieman, Nobel Prize in physics, 2001

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Dept. ECE @ UBC

• 56 faculty members, 11 IEEE Fellows• Two graduate degrees: BASc EE, BASc CE• Three postgraduate degrees: PhD, MASc, MEng

• Approximately 800 undergraduate students (year 2, 3, 4) and 350 graduate students

• Research groups:– Biotechnology Group– Communications Group– Control and Robotics Group– Computer and Software Engineering Group– Electric Power and Energy Systems Group – Microsystems and Nanotechnology Group– Signal Processing and Multimedia Group– Very Large Scale Integration Group

Communications Group @ ECE, UBC• Vijay Bhargava – error correcting codes, wireless systems and

technologies beyond 3G, cognitive radio• Lutz Lampe – modulation and coding, MIMO systems, CDMA,

ultra-wideband (UWB), wireless sensor networks• Cyril Leung – wireless communications, error control coding,

modulation techniques, multiple access, security• Victor Leung – network protocols and management techniques,

wireless networks and mobile systems, vehicular telematics• Dave Michelson - propagation and channel modeling for wireless

communications system design, low-profile antennas• Robert Schober – detection, space-time coding, cooperative

diversity, CDMA, equalization• Vincent Wong – wireless networks, ad hoc, sensor networks

strong research focus on wireless

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My Research Focus• Network architectures, protocols, management algorithms,

modeling and performance evaluations• Two main thrusts:

– Wireless telecom 3G and beyond• Radio resource management for high speed packet access• Interworking of heterogeneous wireless networks • Handoff and mobility management• Quality of service provisioning• Authentication, authorization and accounting

– Networking for license-free wireless communications• Wireless personal area networks• Wireless sensor networks• Vehicular ad hoc networks and vehicle-infrastructure integration• Wireless body area networks• RFID networks

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My Team

• Postdoctoral fellows − Dr. Alireza Attar, Dr. Hongbo Guo, Dr. Sang-Wook Han, Dr. Xuedong Liang

• PhD students − Nasim Arianpoo, Amr Al Asaad, Mohsen Amiri, Javad Hajipour, SeyedAli HosseiniNezhad, Paria Jokar, Pouya Kamalinejad, Haoming Li, Mahmood Minhas, Saad Mahboob, Hasen Nicanfar, Rukhsana Ruby, Bambang Sarif, Jun-Bae Seo, Kaveh Shafiee, Peyman TalebiFard, Narjes Torabi, Jun Wang, Jie Zhang

• MASc students − Wei Bao, Xiaolei Hao, Geoffrey Lo, Madhu Sharma

• Collaborators − Prof. Henry Chan (Polytechnic U. of HK), Prof. Min Chen (SNU Korea), Prof. Jiannong Cao (Polytechnic U. of HK), Prof. Sathish Gopalakrishnan, Dr. Song Guo (Aizu U. Japan), Prof. Hong Ji (BUPT, China), Dr. Zhifeng Jiang (China Netcom), Prof. Vikram Krishnamurthy, Dr. Ki-Dong Lee (LG), Prof. Panos Nasiopoulos, Dr. Qixiang Pang (General Dynamics), Dr. Helen Tang (DRDC), Prof. Son Vuong (UBC CS), Mr. Terrence Wong (Huawei Canada), Prof. Vincent Wong, Prof. Oliver Yang (U. Ottawa), Prof. Fei Yu (Carleton U.), Dr. Yan Zhang (Simula), Prof. Qian Zhang (HKUST), Prof. Yihua Zhu (Zhejiang U.Technology)

Broadband Wireless Access with Fibre-Connected Massively

Distributed Antennas

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RF over Fibre

• Uses low cost uncooled directly-modulated laser diodes• Flat frequency response over wide frequency range• Support transport of wideband analog RF signals over long distances

via optical fibres• Analog signal transport agnostic to air interface standards

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Zinwave 3000 Series DAS

• Commercial version of system developed at Cambridge Photonics Lab.

• Analog signals at Hub distributed to Remote Antenna Units (RAUs) via single mode or multimode fibres (SMF/MMF) or coaxial cables

• Frequency range: 136 – 2700 MHz

• Supports up to 64 RAUs

• Cable distances of more than 550m for MMF and more than 2000m for SMF

Operator 1GW

Operator 2GW

Backbone/Internet

Optical fiber

Antennaelement

Operator 1Central Processing Entity

Coaxial cable or Optical fiber

Operator 2Central Processing Entity

BWA-FMDA Architecture

Distribution Architectures without Fibres

• Examples: femto-cells, pico-cells, mesh networks

• Advantages:

– Reduce power consumption and enhancing spectrum utilization by shortening the links

– Exploit cooperative schemes

– Utilize cognitive mechanisms

• Disadvantages:

– Large overhead for co-ordinations

Distribution Architectures with Fibres

• Components: – A large number of distributed antennas connected via optical fibres

to a centralized processing entity

• Advantage: – minimizing the communication overheads of system co-ordination

• Environments:– Homes and office environments. Covers a few tens of meters.

Service delivered via IEEE 802.11a/g/n and femto-cell hotspot solutions

– Last-mile coverage. Covers several kilometers. Service delivered via WiMAX, LTE and LTE-A

• Frequency bands:– License-free bands: Cognitive WLAN over fibre systems– Licensed bands: CoMP of LTE femto-cells

Source: Global FTTH ranking, Feb. 2011, FFTH council press release.

FTTH Penetration among G20 (Feb. 2011)

Blue: FTTH; Orange: FFTB+LAN

Research Themes in BWA-FMDA

• The fundamental performance limits of massively distributed antenna systems

• Improved measurement-based channel models involving massively distributed antennas

• Advanced radio resource management and access control schemes that approach the performance limits in realistic propagation environments– radio resource management algorithms – medium access control protocols – optimal cooperative relaying– interference alignment techniques

• Improved opto-electronic transceivers designs for low cost active optical cables suitable for RoF applications

BWA-FMDA in License-free Bands: Cognitive WLAN over Fibre System

(CWLANoF)

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CWLANoF System Architecture

RAU

CogAPEthernet

8 fibers

Optical Interface(E/O and O/E)RF / Baseband

Optical Interface(E/O and O/E)RF / Baseband

…

Bridge to 802.3 Ethernet

Central Control

Unit (CCU)

From/toRAU #1

From/toRAU #N

802.11 carrier sensing802.11 MAC

A/D

DSPSpectrum Usage Assessment

Tx / RxDiversity Processing

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CWLANoF vs. Conventional ESS

WLANController

CogAP 2-strand fibers

Digital

AnalogRAU

AP

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CSMA @ central

CSMA @ local APs

ISM Band Users: Power and Frequencies

WLAN2400~2483.5 MHz

WLAN5150~5350 MHz

Bluetooth

Microwaveoven

Cordless phone Cordless phone

WLAN5725~5825 MHz

Pow

er

Zigbee

RFID

Frequencies

UWB

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Motivation of Cognitive Access Point

• Wide variety of independent ISM-band devices

• WLAN over Fiber– Full spectrum available for processing at CogAP– Cognition of “radio landscape” – localization of interference– Avoid or mitigate interference– Multiple RAUs supporting multi-antenna, diversity and

cooperative communications

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Functions of Cognitive Access Point• Receive full spectrum of ISM

band• Receive multiple WLAN

channels• Cooperatively demodulate

user packets received over multiple RAUs

• Identify and localize all sources of interference

• Transmit full spectrum of ISM band

• Transmit multiple WLAN channels

• Cooperatively transmit user packets over multiple RAUs

• Interference mitigation– Cancellation– Avoidance

• Multiple-RAU management– Diversity– Multi-input Multi-output– Beam forming

• Radio resource management– Channel selection– Signalling diversity– Transmission scheduling– Transmit power control

• Connection admission control• Quality of service assurance

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Spectrum Sensing

• Power measurement – Simplest to implement but does not give much information about

the type of interference– Interference mitigation via random backoff and scheduling

• Cyclostationary detection– More complex but more information– Example: pulsing interval of microwave oven, frequency hopping

cycle of Bluetooth radio– Better scheduling and no need to backoff

• Matched filter detection– Need different filters for different types of interference– Positive identification of interference – Facilitate interference mitigation via cancellation

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Station and Service Set Management

• Practical solution must cater to legacy stations supporting existing standards

– Station operates using DCF over a single channel

– Station may be silenced by CogAP via CTS

• Service set management needs reconsideration

– Station may receive from more than one RAUs

– Station may transmit to more than one RAUs

• Advanced solutions may extend the management frame definitions

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Research Issues in CWLANoF

• Objective is to take advantage of the unique features of the proposed architecture by developing novel communication techniques:– New signal processing algorithms

• Spectrum sensing techniques• MIMO• Beam forming• Interference cancellation

– New radio resource management algorithms• Channel and power allocation • Interference avoidance

– New MAC and network management protocols • Performance evaluations challenging due to the dynamic

environments and large degrees of freedom (space, time, frequency)

A Typical CWLANoF System in An Office Building

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Evaluation of CWLANoF with 2 RAUs• Methods:

– Conventional WLAN (a different channel at each AP)– CWLANoF with 2-channels operating independently at each RAU– CWLANoF with 2-channels and uplink maximum ratio combining

between RAUs• Traffic:

– Spatial uniform: Static traffic– Spatial non-uniform: Dynamic traffic

• Simulation environment: NS-2.33 simulator.

f1 f2

Conv. WLAN

f1f2

f1f2

2-channel

f1f2

f1f2

MRC-up

CWLANoF systems

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NS-2.33 Parameters (1)

• Area: 30-by-60 m2

• Propagation: Simplified pathloss + Shadowing +

Rayleigh fading

• IEEE 802.11g (frequency: 2.4 GHz)

• Link rate: Signal-to-noise-ratio-based dynamic rate

adaptation, available in dei80211mr package of NS-2.33

• No RTS/CTS

• Perfect CSI at the CogAP

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NS-2.33 Parameters (2)

* The synchronization interval (SI) is used to control “capturing effect”. When two packets arrive within SI, the receiver will synchronize to the stronger packet.

Propagation

Pathloss exponent = 2.5

Reference distance, d0 = 2 m

Standard deviation of shadowing = 3.5 dB or 10 dB

PHYTransmission power, Pt = 10 mW

Carrier-sensing threshold = -70 dBm

MAC

Synchronization interval = 5 us *

aSlotTime = 20 us

CWMin/Max = 31 / 1023

FTP/TCP traffic TCP/Reno. Packet size = 1000 bytes.

CBR traffic Packet interval 20 ms. The 1000-byte packets for IP-TV; 40-byte packets for VoIP.

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CWLANoF under Spatial Uniform Traffic:10% TCP Throughput Gain

12 14 16 18 20 22 24 26 28 30 320

1

2

3

4

5

6

7

8

TCP

Thr

ough

put (

Mbp

s)

Number of STAs

traffic: two-way VoIP + FTP/TCP download

Conv. WLAN2-Channel-OperatingMRC-up

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STAs for background traffic

STAs in a hotspot location

RAUs

1 2 3

4 5 6

Evaluation of CWLANoF under Spatial Non-uniform Traffic

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1 2 3 4 5 64

4.5

5

5.5

6

6.5

7

7.5

8TC

P th

roug

hput

(Mbp

s)

Hotspot location

Shadowing St.Dev. = 10 dB

Conv. WLANMRC-up2-Channel-Operating

CWLANoF under Spatial Non-uniform Traffic: 33% TCP Throughput Gain

Traffic: VoIP uplink/downlink + FTP downlink).

BWA-FMDA in Licensed Bands: CoMP of LTE Femto-cells

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LTE HetNet Architecture

Motivations

• Shortening the last mile access towards femtocells provides better utilization of resources and higher throughputs

• No X2 interface for femto BSs in 3GPP LTE/LTE-A provisioned– Coordinated resource allocation and interference mitigation is not

feasible (to/from macro BS & neighbor femto BSs)– More challenging in dense urban scenarios

• Potential of energy consumption saving if more users can be served with fewer access nodes– Cooperative schemes also enhance the performance compared with a

group of independent access nodes

• BWA-FMDA provides Coordinated MultiPoint (CoMP) transmission at femtocell level

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Frequency Reuse Cases

• HetNet-F1: Universal frequency reuse under independent-HetNet regimes

• HetNet-F2: Devices in adjacent rooms (on the same floor and on adjacent floors) use different frequencies, operating over independent-HetNet systems

• 6-CoMP F2: Six HeNBs on each floor form a femto-CoMP using the same frequency as 2 floors above and 2 floors below, while femto-CoMPs on adjacent floors use different frequencies

• 6-CoMP F4: Six HeNBs on each floor form a femto-CoMP while femto-CoMPs located on different floors use different frequencies

• 12-CoMP F2: Twelve HeNBs on every two floors form a femto-CoMP; however, adjacent femto-CoMPs use different frequencies

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Cluster 1

Cluster 2

Cluster 3

Cluster 4

Cluster 1

Cluster 2

Cluster 3

Cluster 4

BWA-FMDA

12m

36m

6m14m

2m

Cluster 2

Cluster 1

6-CoMP F2 6-CoMP F4 12-CoMP F2

Freq-1

Freq-2

Freq-4

Freq-3

officefloor

hallcluster

Legend

Femtocell (1-AE)AE

UE

Floor layout: Dual-stripe. Room height: 3 meters.

dUE

HetNet-F1 HetNet-F2

Simulation Parameters

• Zero-forcing beamforming

• Perfect CSI at the central processing entity

• Traffic: Downlink only. Saturated

• Simulation time: 5 seconds

• Pathloss and shadowing model: ITU M.1225 with the penetration loss model from COST231, i.e., 18.3 dB loss per floor and 6.9 dB loss per wall

• Frequency-selective fading. 1.4 MHz channel (1.08 MHz signal/noise bandwidth)

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2 3 40

0.5

1

1.5

2

2.5

3

3.5

Ave

rage

d U

E th

roug

hput

(Mbp

s/ch

anne

l)

UE density (Number of UEs per room)

HetNet-F16-CoMP-F2 robinT-wI

CoMP Provides 50% Throughput Gain

40

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CoMP Provides Better Fairness

0 2 4 6 8 10 120

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

UE throughput (Mbps/channel)

CD

F HetNet-F1HetNet-F26-CoMP-F2 robinT-wI6-CoMP-F4 PF-search6-CoMP-F4 PF-SUS6-CoMP-F4 robin-SUS6-CoMP-F4 robinT12-CoMP-F2 PF-SUS12-CoMP-F2 robin-SUS12-CoMP-F2 robinT

CDF of UE throughput. Assume two UEs per room.

0 0.002 0.004 0.006 0.008 0.010

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Scheduling delay (seconds)

CD

F

HetNet-F1 (2UE)HetNet-F1 (3UE)HetNet-F1 (4UE)6-CoMP-F2 robinT-wI(2UE)6-CoMP-F2 robinT-wI(3UE)6-CoMP-F2 robinT-wI(4UE)

CoMP Provides Bounded Scheduling Delay

Scheduling delay: the number of time slots between two consecutive transmissions.

HetNet-F1

CoMP

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Research Issues in CoMP of LTE Femto-cells

• Novel scheduling and interference management in LTE-A

• Adapting the architecture to 3GPP HetNet model

• Green communication schemes:

– Adaptive CoMP in BWA-FMDA to reduce signal processing power consumption

– Dynamically turning off RAUs to save energy

– Shifting towards active fiber backbones to further save energy

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BWA-FMDA Testbed

• Testbed consists of Zinwave DAS and powerful DSP-based SDR platform

• CDN$150K Research Tools and Instruments grant approved• Research on radio management issues in progress

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• Fibre-connected Massively Distributed Antennas (FMDA) leverages recent advances in RF over fibre technology to provide Broadband Wireless Access (BWA) in both license-free and licensed bands

• License-free: FMDA enables the application of cognitive principles in cognitive WLAN over fibre systems to offer equal access in ISM band

• Licensed: FMDA enables CoMP in LTE femto-cells to increase system capacity, provide better fairness, and consume less power

• BWA-FMDA architecture leads to many new research problems

• Expect many innovative research results and commercial products to emerge over the next few years

Conclusions

Thank you!

www.ece.ubc.ca/~vleungvleung@ece.ubc.ca