bridging the theory – practice gap in wireless research...
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WINLAB
Bridging the Theory – Practice Gap in Wireless Research
EDGE Lab Open House Princeton, April 28, 2011
Prof. D. Raychaudhuri
WINLAB, Rutgers University Technology Centre of NJ
671 Route 1, North Brunswick, NJ 08902, USA
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Introduction
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Introduction: Wireless Technology at a Historic Inflection Point
• Ongoing shift from wired PC’s to mobile computing and embedded devices… – ~4 B cell phones vs. ~1B Internet-connected PC’s in 2010 – Mobile data growing exponentially – Cisco white paper predicts
>1exabyte per month (surpassing wired PC traffic) by 2012 – Sensor deployment just starting, ~5-10B units by 2020
INTERNET
Wireless Edge Network
INTERNET
~1B server/PC’s, ~700M smart phones
~2B servers/PC’s, ~10B notebooks, PDA’s, smart phones, sensors
~2010 ~2020
Wireless Edge Network
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Mobile Data Traffic Swells 193% You can thank the iPhone for leading the charge when it comes to a massive deluge of new mobile Internet traffic. March 26, 2010
Eric Schmidt: smartphones are the future for Google and the world
The chief executive of the search giant believes smartphones will empower the poor and is the equivalent to the arrival of TV Guardian UK, 28 June, 2010
At AT&T, the No.2 wireless carrier in the United States, after Verizon Wireless, the use of mobile data surged 5,000 percent from 2007 through 2009 after the operator became the exclusive U.S. seller of Apple’s iPhone, which has helped popularize the mobile Web. But it has also strained AT&T’s wireless network at peak times in urban areas in New York and California. April 18, 2010
Getting What You Pay For on the Mobile Internet
Broadband Availability to Expand The Obama administration is seeking to nearly double the wireless communications spectrum available for commercial use over the next 10 years, an effort that could greatly enhance the ability of consumers to send and receive video and data with smartphones and other hand-held devices. June 27, 2010
Cutting the cord on Internet Connection Research indicates that 56 percent of users connect to the internet wirelessly. Jul 23, 2009
Mobile Internet exploding, online ads about to take off, In the Morgan Stanley analyst’s presentation at the Conversational Marketing Summit in New York, Meeker said mobile Internet use is ramping up faster than desktop Internet use did, with Apple leading the trend with the release of the iPhone nearly three years ago.
Introduction: Wireless Technology at a Historic Inflection Point (cont.)
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Introduction: Implications for Wireless R&D n Mass-market adoption of wireless technology has important
implications for research & development ¨ Fundamental challenges of scale, capacity and spectrum use ¨ “Moore’s Law” for wireless technology à faster product cycles ¨ Trend towards uniform core technologies, e.g. SDR ¨ Architectural convergence with the Internet (protocols, software, apps,..)
n Wireless R&D methodology of the ~1990’s-2000’s not well suited to meet these challenges ¨ Historically separate development of radio & network technology ¨ Split between theory and experimentation in both these fields ¨ ~7-10 yrs gestation period from early information/comm theory ideas to
practical realization ¨ Theory & simulation (2-3 yrs) à lab experiments (2-3 yrs) à field trial technology
(2-3 yrs) à ASIC (1-2 yrs) à commercial products ¨ Urgent need for modernization of R&D process to meet market demand!
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Introduction: Wireless R&D Challenges circa 2010
Static Spectrum Assignment
Dynamic Spectrum Assignment
~10x eficiency
Single User MIMO/OFDM
Next-Gen Gigabit PHY
Static MAC Protocols
Flexible & Adaptive MAC
IP Routing + Cellular Mobility
Mobility-Centric Internet Arch
Mobile web services
Content- and context-aware pervasive
services
Spectrum sensing, NC-OFDM, Spectrum server, cognitive algorithms, Coordination protocols, ..
Network MIMO, network coding, interference alignment, 60 Ghz,
Cooperative relay, cross-layer, beam switching, software MAC,..
Storage-aware routing, global name resolution, location, ad hoc/DTN routing, …
Content- and context-aware protocols, Programmable networks, cloud services, …
~2010’s technology ~2020
Significant Evaluation & Validation Challenges For the R&D Community!
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Introduction: The Theory-Practice Gap
Theoretical Models
Time
Increasing Realism
“Small” Radio Expts
Simulation Models
System-Level Prototype
Product Beta Trials
ASIC
“The Gap” Laboratory Prototypes
Basic Research (mostly at universities)
Applied Research (mostly at companies)
Can this gap be closed, speeding up the R&D cycle and improving feedback?
Large-Scale/Accurate Simulations
Feedback Loop (delay~3-5 yrs)
0 5 yrs 10 yrs
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Bridging the Theory-Practice Gap
New Experimental Platforms & Testbeds
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Introduction: Wireless R&D Methodology ~2000-10
Degree of Realism
Scale
Math models
Opnet or ns Simulator
FPGA Prototype
Lab Prototype
PHY/MAC ASIC
Field Trial System
Academia & basic research
labs
Industry
~$100K
~$10M
$10K
~$25M
~$100M
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Introduction: Advances in Wireless R&D Platforms & Testbeds for Academic Research ~2010
Degree of Realism
Scale
Math models
Network Science
Opnet or ns Simulator
WINLAB ORBIT Radio Grid Emulator
Open Cellular Campus Testbeds
GENI Core Network
CO-WINLAB CR Platform USRP2 USRP/GNU Radio
CMU Radio Emulator
SDR Sandbox in ORBIT ~$1K
~$10K/free
~$10M (free shared access)
~$2M (shared access)
~$50M (shared access)
~$2M (shared access)
~$10K ~$10K
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Experimental Platforms: Software Radios
WINLAB WINC2R System RST SDR System USRP2
USRP
RICE WARP Platform U. Of Colorado
SDR represent a fundamental change in PHY/MAC design methodology, Eliminating the ASIC phase, and broadening access to students with software-only training. Makes it possible for researchers to explore clean slate wireless ideas with real hardware!
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Example SDR Experiment: Adaptive MAC
• Global Control Plane : WiFi Data Plane : GNUradio (USRP)
• TDMA time slot set up as 300ms for pktsize = 1500B and 100ms for pktsize = 500B (RTT + Processing Time)
Data Plane (GNUradio)
PHY type GMSK
Operating FREQ 400MHz
PHY rate 50kbps
MAC type CSMA/TDMA
Transport Protocol
(1). UDP with CBR (25, 50, 75Kbps and packet size of 500B and 1500B)
(2). TCP (3) UDP with CBR 25Kbps
and mix packet size of 100B and 1500B
GNUradio 802.11b
Node1 Node2
Node3 Node4
GNUradio 802.11b
GNUradio 802.11b
GNUradio 802.11b
60 feet
60 feet
60 feet
60 feet
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Example SDR Experiment: Adaptive MAC (cont.)
UDP with pkt=1500B
0%
20%
40%
60%
80%
TDMA
CSMA
AMAC
TDMA
CSMA
AMAC
TDMA
CSMA
AMAC
25kbps 50kbps 75kbps
Throughput
Node pair 1
Node pair 2
UDP with pkt=500B
0%5%10%15%
20%25%30%
TDMA
CSMA
AMAC
TDMA
CSMA
AMAC
TDMA
CSMA
AMAC
25kbps 50kbps 75kbps
Throughput
Node pair 1
Node pair 2
UDP with traffic load 25kbps
0
5000
10000
15000
20000
25000
30000
5 20 35 50 65 80 95 110125140
Transmitted packet number
Throughput(bps)
CSMA
TDMA
AMAC
Switch
• AMAC is able to adapt to better performance MAC based on throughput drop (if drop >20%, request switch)
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Example SDR Experiment : Secondary Coexistence In White Space
WS Mobile Access Protocol
WS AP w/ backhaul
Secondary System A Secondary System B
freq
Secondary A Spectrum
Secondary B Spectrum
• Secondary co-existence an important requirement for white space bands • Various schemes possible depending on system model
– Completely autonomous, using performance feedback only – Common coordination channel – Common Internet based spectrum server
Common Coordination Channel (optional)
Internet
Spectrum Server (optional)
Control information
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Example SDR Experiment : Secondary Coexistence – NC-OFDMA with Interference Suppression
Experiment conducted by Y. Futatsugi & M. Ariyoshi, NEC and S. Pingapany, WINLAB (reported in IEICE Tech Rep, May 2010)
GNU/USRP2 based experimental evaluation of NC-OFDM secondary service with dynamic interference suppression (IA-PFT)
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Experimental Platforms: ORBIT Radio Grid Testbed for Next-Gen Wireless Research
n ORBIT radio grid testbed (released 2005) is an NSF community resource supporting at-scale/reproducible experiments via a web portal www.orbit-lab.org
n 500+ user groups worldwide, ~40,000 experiment to date, ~100’s of papers on topics ranging from spectrum to ad hoc networks to security
n Experimenter control of topology, protocols, radio and network node software; scripting and measurement tools for ease of use
n Open WiFi, BT, Zigbee and SDR radio nodes (over 800 in total)
Urban
300 meters
500 meters
Suburban
20 meters
ORBIT Radio Grid
Office
30 meters
Radio Mapping Concept for ORBIT Emulator
400-node Radio Grid Facility at WINLAB Tech Center
Programmable ORBIT radio node
URSP2 SDR board
Current ORBIT sandbox with GNU radio
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VoIP over WiFi using a Bluetooth headset
Voice quality degradation due to co-located radios
ZigBee Alarm system co-existent with high rate streaming links
Alarm system messages blocked by WiFi
streaming video traffic
Bluetooth links near 802.11b WiFi link
Throughput: 4.92 Mbps
Throughput: 1.92 Mbps
Throughput: 0.42 Mbps
Bluetooth causes a large drop in WiFi throughput
ORBIT Experiment Example 1: Multi-Radio Interference in Home Networks
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Mul$-‐radio Interference Example
ORBIT Experiment Example 1: Multi-Radio Interference in Home Networks (cont.)
ORBIT Measurements
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ORBIT Experiment Example 2: Storage-Aware Routing (CNF, MobilityFirst)
• Storage aware (CNF, generalized DTN) routing exploits in-network storage to deal with varying link quality and disconnection
• Routing algorithm adapts seamlessly adapts from switching (good path) to store-and-forward (poor link BW/disconnected)
• Storage has benefits for wired networks as well..
Storage Router
Low BW cellular link
Mobile Device trajectory
High BW WiFi link
Temporary Storage at Router
Initial Routing Path
Re-routed path For delivery
Sample CNF routing result from ns2 simulation
PDU
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ORBIT Experiment Example 2: Storage-Aware Routing (CNF, MobilityFirst) – cont.
• Poisson arrival process
• File size 500KB
20
p 3 simultaneous flows
p 100 file transfers
p Average throughput
ORBIT Expt Topology
ORBIT Measurement Results
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21
Experimental Platforms: Open 4G/Cellular Base Station (WiMAX)
Outdoor Unit (ODU)
RF Module ( sector)
Base Module
Omni-directional antenna (elev. < 6ft above roof!)
Open WiMAX Base Station deployed at Rutgers as part of ORBIT/GENI Outdoor Trial Network à also at 6 additional campus sites by 2011
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22
Open WiMAX Experiment Example: Virtual Base Station Resource Control
• Design Goals: – Multiple independent virtual
networks (VNs), each with specified % of BS capacity
• Inter-slice fairness & isolation
– For GENI experiments, each VN should be qualitatively equivalent to a dedicated BS
– Each VN (slice) should support multiple clients
• Intra-slice fairness • Multiple traffic types
Phys
ical
802
.16e
BS
10 %
30 %
20 %
Slice1 Slice2 Slice3
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Open WiMAX Experiment Example: Virtual Base Station Resource Control
• VN traffic shaping (VNTS) on external GENI controller • Maintains fairness & isolation between slices • Uses SNMP status feedback (MCS, rate,..) from BS
No Shaping
VNTS
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Concluding Remarks
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Concluding Remarks: n Mass market adoption of wireless technologies implies the need for
faster and better R&D methodologies n Earlier approach of separated analysis/simulation & prototyping/product
trials resulted in a theory-practice “gap” n This gap can be closed via innovations in experimental platforms which
provide flexibility, scale and low-cost access n WINLAB has recognized this need since ~2000, and has pioneered
design and development of experimental platforms for wireless R&D n Cognitive radio/SDR platforms (..flexible hardware for PHY/MAC research)
n ORBIT radio grid testbed (…large-scale, reproducible network performance) n Open 4G base station (…real-world mobile network/service studies) n GENI networking infrastructure (…evaluation of global Internet architectures)
n These experimental systems (and similar innovations by other groups) help to close the theory-experiment gap, improving researcher access and reducing design cycle times from ~7-10 yrs to ~3-5 yrs
n In the long run, we hope to change the culture of academic research to incorporate hands-on experimentation by graduate students & faculty..