Adaptive Wireless Networks Using Cognitive … Wireless Networks Using Cognitive Radios as a Building Block MobiCom2004 KeynoteSpeech Sept 29, Philadelphia D. Raychaudhuri Professor
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Adaptive Wireless Networks Using Cognitive Radios as a Building BlockMobiCom 2004 Keynote SpeechSept 29, Philadelphia
D. RaychaudhuriProfessor ECE Dept & Director, WINLAB
Rutgers Universityray@winlab.rutgers.eduwww.winlab.rutgers.edu
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Talk Outline
Introduction: the future wireless network and related R&D challengesDynamic spectrum management & cognitive radio conceptsCognitive radio technologies: selected results
Coexistence of 802.11 and 802.16 in unlicensed bandsCSCC spectrum etiquetteAdaptive networks and ad-hoc self-organizationCognitive radio hardware
Concluding remarks
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Introduction
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Introduction: Future Wireless Network Scenario
Internet (IP-based)
Infostationcache
WLANAccess Point
WLANHot-Spot
VOIP(multi-mode)
Low-tier clusters(e.g. low power 802.11 sensor)
Ad-hocnetwork
extension
Public Switched Network(PSTN)
BTS
High-speed data & VOIP
Broadband Media cluster(e.g. UWB or MIMO)
BTS
BSC
MSC
CustomMobileInfrastructure(e.g. GSM, 3G)
CDMA, GSMor 3G radio access network
Generic mobile infrastructure
Today Future
GGSN,etc.
Voice(legacy)
High-speed data & VOIP
Relay node
Growing role for fast, low-costshort-range radios
Heterogeneous systems with multipleradio standards (3G, 4G, WLAN, UWB..)
Self-organizing ad-hoc access networksIncreasing use of unlicensed spectrum
and dynamic sharing methodsUniform IP core networkWide range of applications (
“ubiquitous wireless services”)
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Introduction: Wireless Technology TrendsPervasive systems
~1 Mbps 3G/WCDMA~10-54 Mbps WLAN
~100 Mbps+4G/OFDM, 802.16 &
WLAN;~500 Mbps UWB, etc
IP-based networksfor both
Cellular & WLAN
IP+ Layer 7 overlayinfrastructure net;
Ad-hoc low-tiernetworks
Telephony;Multimedia;
Mobile Internet
Telephony; Multimedia;
Mobile InternetSensor Nets
Telephony;PC/LAN
PrimaryApplications
RadioTechnology
NetworkArchitecture
2G/CDMA & TDMA~1 Mbps WLAN
Cellular networksEthernet + WLAN
~1995-2000 ~2000-2005 ~2010+
Beyond IP networks(e.g. content aware routing)
Cross-layer techniques
Self-organizing multi-hop
Sensor net applications,Embedded wireless devices
VOIP, H264, HTTP, etc.Location-aware services
Mobile IPv6, etc.
Higher speed,OFDM Very wideband signals
New spectrum policiesCognitive radio
Adaptive RadioNetworks
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Introduction: Key Technologies for Future Wireless Systems
New radios for heterogeneous accessLow-power sensor radiosHigh-speed WLAN and 4G/802.16Faster 4G cellular, 802.16, etc.
Spectrum-sharing for dense networksDynamic spectrum/cognitive radio for frequency coordinationSpectrum etiquette protocols
Ad-hoc wireless networksSelf-organizing networks capable of scaling organicallyDiscovery, MAC and routing protocols for reliable ad-hoc services
Pervasive computing softwareDynamic binding of application agents and sensorsReal-time orchestration of sensors and actuators
Focus of this talk
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Dynamic Spectrum Management & Cognitive Radio
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Motivation for Dynamic Spectrum and Cognitive Radio Techniques:Static allocation of spectrum is inefficient
Slow, expensive process that cannot keep up with technology
Spectrum allocation rules that encourage innovation & efficiencyFree markets for spectrum, more unlicensed bands, new services, etc.
Anecdotal evidence of WLAN spectrum congestionUnlicensed systems need to scale and manage user “QoS”
Density of wireless devices will continue to increase~10x with home gadgets, ~100x with sensors/pervasive computing
Interoperability between proliferating radio standardsProgrammable radios that can form cooperating networks across multiple PHY’s
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Spectrum Management: Frequency allocation today …
Source: FCC website
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Spectrum Management: Policy ConceptsUnlicensed bands with spectrum etiquette
More ISM/U-NII bands with simple coordination rules
Property RightsFee simple ownership with non-interference easements
Spectrum clearinghousePackets are sent with access tokens with pricing determined by congestion
Open accessNo coordination rules, technology expected to evolve towards co-existence
Cognitive radio bandsAgile/smart radios capable of adaptive strategies for interference avoidance
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Spectrum Management: Problem ScopeSpectrumAllocation
Rules(static)
INTERNET
BTS
AuctionServer
(dynamic)
SpectrumCoordination
Server(dynamic)
AP
Ad-hocsensor cluster(low-power, high density)
Short-rangeinfrastructure
mode network (e.g. WLAN)
Short-range ad-hoc net
Wide-area infrastructuremode network (e.g. 802.16)
Dense deployment of wireless devices, both wide-area and short-rangeProliferation of multiple radio technologies, e.g. 802.11a,b,g, UWB, 802.16, 4G, etc.How should spectrum allocation rules evolve to achieve high efficiency?Available options include:
Agile radios (interference avoidance)Dynamic centralized allocation methodsDistributed spectrum coordination (etiquette)Collaborative ad-hoc networks
Etiquettepolicy
SpectrumCoordination
protocols
Spectrum Coordinationprotocols
Dynamic frequencyprovisioning
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Cognitive Radio: DefinitionsThe term “cognitive radio” used to denote new generation of adaptive wireless devices capable of dynamic spectrum coordination
Baseline capability includes spectrum scanning and frequency agilityFast adaptation of transmitted signal to fit into changing radio environmentCapable of higher-layer spectrum etiquette or negotiation protocolsMay also participate in ad-hoc networks formed with other cognitive radiosInteroperability with multiple radio technologies based on SDR capabilities
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Cognitive Radio: R&D Status
Policy and technology R&D on cognitive radio still at an early stage. Recent activities include:
FCC notice of rulemaking for specific “underlay” data services in UHF TV bandsMore general notice of proposed rulemaking on new unlicensed cognitive bandsSoftware defined cognitive radios developed at Vanu Inc., GNU/UtahXG policy framework being developed by DARPASystem studies and prototyping at Mitre, Rutgers/WINLAB, Stevens, others….New National Science Foundation research initiative (“NeTS ProWIN”), 2004
Cognitive radio has the potential for significant improvements in spectrum efficiency, performance and interoperability between unlicensed band services
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Cognitive Radio: Design SpaceBroad range of technology & related policy options for spectrum
Need to determine performance (e.g. bps/Hz or bps/sq-m/Hz) of different technologies taking into account economic factors such as static efficiency, dynamic efficiency & innovation premium
Hardware Complexity
Protocol Complexity(degree of
coordination)
ReactiveRate/Power
Control
ReactiveRate/Power
Control
AgileWideband
Radios
AgileWideband
Radios
Unlicensed Band
with DCA (e.g. 802.11x)
Unlicensed Band
with DCA (e.g. 802.11x)
InternetServer-based
SpectrumEtiquette
InternetServer-based
SpectrumEtiquette
Ad-hoc,Multi-hop
Collaboration
Ad-hoc,Multi-hop
Collaboration
Radio-levelSpectrumEtiquetteProtocol
Radio-levelSpectrumEtiquetteProtocol
StaticAssignmentStatic
Assignment
InternetSpectrumLeasing
InternetSpectrumLeasing
“cognitive radio”schemes
UWB,Spread
Spectrum
UWB,Spread
Spectrum
“Open Access”+ smart radios
Unlicensed band +simple coord protocols
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Reactive (autonomous) methods may be used to avoid interference via:
Frequency agility: dynamic channel allocation by scanningPower control: power control by interference detection and scanningTime scheduling: MAC packet re-scheduling based on observed activity
A
D
C&D’s spectrum bandRange with Power Control
A
BB
C
DA&B’s spectrum band
Range without Power Control
Range without Power Control
Range with Power Control
Cognitive Radio: Reactive Algorithms
Frequencyagility DD DC
Scheduling
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Cognitive Radio: Limitations of Reactive Schemes
Reactive schemes (without explicit coordination protocols) suffer from certain limitations:
Near-far problems possible at the receiverInability to predict future behavior of other nodesOnly detects transmitters, not receivers, but interference is a receiver property
Coverage area of D
Y
A
B
C
D
A cannot hear DA’s agile radio waveform
D’s agile radio waveformwithout coordination protocol
with coordination
Hidden Terminal Problem
Coverage area of A
Coverage area of D
Y
A
B
C
D
A cannot hear DA’s agile radio waveform
D’s agile radio waveformwithout coordination protocol
with coordination
Hidden Terminal Problem
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Cognitive Radio: Spectrum Policy ServerInternetInternet--based Spectrum Policy Serverbased Spectrum Policy Server can help to coordinate wireless networks
Needs connection to Internet even under congested conditions (...low bit-rate OK)Some level of position determination needed (..coarse location OK?)Spectrum coordination achieved via etiquette protocol centralized at server
InternetInternet
Access Point(AP2)
AP1
WLANoperator A WLAN
operator B
Ad-hocBluetoothPiconet
Wide-areaCellular data
service
SpectrumPolicy Server
www.spectrum.netAP1: type, loc, freq, pwrAP2: type, loc, freq, pwrBT MN: type, loc, freq, pwr
MasterNode
EtiquetteProtocol
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Cognitive Radio: Common Spectrum Coordination Channel (CSCC)
Common spectrum coordination channel (CSCC) Common spectrum coordination channel (CSCC) can be used to coordinate radios with different PHY
Requires a standardized out-of-band etiquette channel & protocolPeriodic tx of radio parameters on CSCC, higher power to reach hidden nodesLocal contentions resolved via etiquette policies (..independent of protocol)Also supports ad-hoc multi-hop routing associations
Frequency
CH#N
CH#N-1
CH#N-2
CH#2
CH#1
CSCC
::
Ad-hocnet B Ad-hoc
net A
Ad-hocPiconet
MasterNode
CSCCRX range
for X
CSCCRX range
for Y
Y
X
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Adaptive Wireless Networks: Ad-Hoc CollaborationCognitive radios can organize themselves into a multia multi--hop adaptive hop adaptive network network in order to achieve better system performance
Multi-hop collaboration can increase spectrum efficiency, reduce powerconsumption and potentially also improve throughput Cognitive radio scans for active nodes and executes discovery algorithmBootstrapped PHY to selected nodes adapts to high bit-rate, low power/rangeControl protocol between nodes used to negotiate ad-hoc network parameters and to exchange routing tables
PHY A
PHY BPHY C
Control(e.g. CSCC)
Multi-mode radio PHYAd-Hoc Discovery
& Routing Capability
AA
BB
D
C
D
E
F
Bootstrapped PHY &control link
End-to-end routed pathFrom A to F
Adaptive WirelessNetwork Node
(…functionality can be quitechallenging!)
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Adaptive Wireless Network: Simple cellular/WLAN example
Multi-mode (cellular, WLAN) or cognitive radio capable of ad-hoc association can be used to improve cellular srevicesSystem may also include provisioned “radio forwarding nodes”Radio paths (single or multi-hop) selected adaptively based on current cellular radio link quality and proximity to other nodes
BTS
ForwardingNode
Dual-ModeMobile
(relay node)
Dual-ModeMobile Ad-Hoc
Cluster 1
To wirednetwork
To wirednetwork Ad-Hoc
Cluster 2
Ad-HocCluster n
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Cognitive Radio Techniques: Selected Research Results
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Reactive Schemes: Case study of 802.11 & 16 in shared unlicensed band
802.11b(~500m) and 802.16a (~10Km) coexist by applying reactive schemes to avoid interference
Dynamic Frequency Selection (DFS):Radio Scans each channel and calculates interference power levelTypical scanning interval is averaged 100msChoose the channel with least interference for communication
Power Control (PC):The receiver senses interference power level and calculates the minimum required transmit power and feedback to the transmitterThe transmitter uses minimum transmit power for communication
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802.11 & 16 Co-Existence: Simulation Parameters
802.16a 802.11bTraffic Type UBR (Poisson arrival), UDP packet, 512 Bytes datagram
MAC protocol TDMA IEEE 802.11 BSS modeChannel Model AWGN, two ray ground propagation model, no fading
Default channel Channel 1 : centered at 2412GHz Channel 1 : centered at 2412GHzAvailable channels 4 (non-overlap) 12 (overlapping)
Bandwidth/channels 20 MHz / 4 non-overlapping chs 22MHz / 11 overlapping chs
Receiver Sensitivity -80dBm (@BER 10^-6) -82dBm (@BER 10^-5)Antenna Height BS 15m, SS 1.5m 1.5m
Tx Power/Max range 33dBm / 3.2Km 20dBm / 500m
Bit Rate 13Mbps 2MbpsRadio parameters OFDM (256-FFT, QPSK) DSSS (QPSK)Background Noise -174 dBm/Hz
Rx Noise Figure 9 dB 9 dB
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802.11 & 16 Co-Existence: Power Control ResultsObservations:
802.16 throughput can improve up to 3 times at the expense of 802.11 throughput degradation < 10% (e.g. at D=2.5Km)If two systems are too near to each other, power control may not work
4 links for 802.11 hotspot, each has Poisson arrival with mean 3ms802.11 hotspot is 3Km away from 802.16 BS
2000 2200 2400 2600 2800 30000
50
100
150
200
250
300
350
400
450
802.
16 D
L Th
roug
hput
(Kbp
s)
802.16 BS-SS Distance (meters)
Both PC OFF Both PC ON
2000 2200 2400 2600 2800 3000
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
802.
11 h
otsp
ot A
vera
ge L
ink
thro
ughp
ut (M
bps)
802.16 BS-SS Distance (meters)
Both PC OFF Both PC ON
802.16 Down Link Throughput 802.11 Average Link Throughput
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CSCC Spectrum Etiquette ProtocolCSCC( Common Spectrum Coordination Channel) can enable mutual observation between neighboring radio devices by periodically broadcasting spectrum usage information
Service channels
Edge-of-bandcoordination channel
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CSCC: Protocol Stack
CSCC-PHY: 1Mbps 802.11b with 10 mW power (~100 m range)
CSCC-MAC: Simple periodic broadcast with randomization (100ms~seconds) to eliminate repeated collisions
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CSCC: Packet FormatDestaddr
Srcaddr
Type IE length IE(1) IE(n)
6B 6B 2B 2B 2B 2B
CSCC-PKT: A standard Ethernet packet format with control payload (consisting of variable length information elements)
. . . Duration (32b)
Service Time . . .Price_bid(8b)Priority (8b)
Channel(8b)Type (8b). . . and Description
. . . Device Name and Description (64bits) . . .
Device Name and . . .. . . MAC Address
CSCC radio (802.11) MAC Address (48bits). . .
0 8 16 24 31
Tx Pwr (8b) Rx Pwr (8b)
CSCC packet used in WLAN-Bluetooth prototype at WINLAB
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CSCC: Proof-of-Concept Experiments
WLAN-BT Scenario
Different devices with dual mode radios running CSCCd=4 meters are kept constantPriority-based etiquette policy
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CSCC: Experimental Parameters
WLAN nodes Bluetooth nodes
Mobility Static without mobility BT1 static, BT2 position varies
Traffic Model 100M bytes data by TCP 1.5M bytes data using Stop-and-wait scheme
MAC protocol IEEE 802.11b at 11Mbps Bluetooth ACL data link
Data card Cisco Aironet 350 series DS (at channel #1)
Ericsson BT w/ USB(hopping over whole band)
CSCC MAC IEEE 802.11 & periodic announcements at 1Mbps
CSCC card Cisco Aironet 350 series DS (at channel #11)
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CSCC Results: Throughput TracesObservations:
WLAN session throughput can improve ~35% by CSCC coordinationBT session throughput can improve ~25% by CSCC coordination
0 20 40 60 80 100 120 140 160 180 200 220 240
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
WLA
N T
hrou
ghpu
t (M
bps)
Time (Seconds)
CSCC on CSCC off
WLAN session with BT2 in initial position
WLAN = high priority
0 50 100 150 200 250 30030
35
40
45
50
55
60
65
Blue
toot
h Th
roug
hput
(Kbp
s)
Time (Seconds)
CSCC on CSCC off
BT session with BT2 in initial position
Bluetooth = high priority
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Adaptive Wireless Networks:Ad-hoc Discovery and Self-Organization
Spectrum etiquette channel used to initiate discovery and network bootstrapExpanded beacon signals transmitted by each radio in CSCCNote that each link may use a different PHY/MAC -> cognitive radio switches between links dynamically, while using mutually agreed routing protocol
D
C
A
B’s transmissionrange
End-to-end routed pathFrom A to D
B
C’s transmissionrange
B’s beacon(may bein CSCC)
C’s beacon(may bein CSCC)
D
Node ID PHY spec MAC spec NeighbortableTx power Routing
bootstrapExample of Beacon Payload
PHY A(~50 Mbps)
PHY B(~100 Mbps) Control connection
Data path
….
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TransmitPower
HopsToAP
NodeType
SequenceNumber
Cluster ID
PacketType
NodeID
BroadcastMAC
SourceMAC
Beacon Frame Format
Low-tier access links(AP/FN Beacons, MN Associations, Data)
Ad-hoc infrastructure links between FNs and APs(AP/FN Beacons, FN Associations, Routing Exchanges, Data)
Forwarding Node (FN)
Access Point (AP)
FN
AP
FNcoverage
area
APcoverage
area
Low-tier(e.g. sensor)Mobile Node (MN)
FN
Self-organized ad-hoc network
MN
MN
MN
MN
MN
MNMN MN
Internet
FN
AP
Channel 4
Channel 2
Beacon
Transmit Power Required: 1mW
Beacon
Assoc
Transmit Power Required: 4mW
FN
AP
SN•Scan all channels•Associate with FN/AP•Send data
FN•Scan all channels•Find minimum delay links to AP•Set up routes to AP•Send beacons•Forward SN data
Adaptive Networks: Ad-hoc Discovery Protocol Implementation
WINLAB’s “SOHAN” 802.11-based ad-hoc prototype demonstrates aspects of self-organization that can be extended to cognitive radio
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Adaptive Networks: Discovery Algorithm Performance Results
NS-2 extended to supportHierarchical net with APs, FNs, MNsMultiple interfacesMultiple 802.11 channels
Distributed and optimal centralized algorithms2 APs, 4 FNs, 10 SNsCBR traffic of 64 byte packets1000 m x 1000 m area1 Mbps 802.11 radios
..significant reductions in routing overhead & energy used
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Adaptive Networks: Ad-Hoc Routing/Discovery Implementation
Protocol stack at each layer
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Adaptive Networks : “SOHAN”Experimental Results
Experimental Setup
Packet delivery ratioGains in system capacity and per-user throughput achievable relative to WLAN BSS mode or comparable “flat”ad-hoc mesh, particularly when FN’suse multiple radio channels...
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Cognitive Radio: Hardware Platforms
Next-generation software-defined radio supporting fast spectrum scanning, adaptive control of modulation waveforms and collaborative network processingFacilitates efficient unlicensed band coordination and multi-standard compatibility between radio devices
MPC8260
TMS320C6701XC2V6000FPGA
100BaseT EthernetMegarray
Connector-244 Configurable
I/O pins
Bell Laboratories Software Defined Radio (Baseband Processor)Courtesy of Dr. T. Sizer
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Cognitive Radio: Hardware PlatformsVanu Inc. SDR programmable radio based on commodity processors. Supports multiple standards on handheld device.
Vanu Inc. Software Defined Radio Source: http://www.vanu.com/products.html
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Cognitive Radio: Hardware Platform
radio
BasebandFPGA
BasebandProcessor Core
(DSP)
SRAM
PacketFPGA
Clock Mgmt
A/D
D/A
A/D
D/A
A/D
D/A
Wakeup
Packet BufferDRAM)
Host(CR Strategies)
radio
radio
Local ethernet drop
Requirements include:~Ghz spectrum scanning,- Etiquette policy processing- PHY layer adaptation (per pkt)- Ad-hoc network discovery- Multi-hop routing ~100 Mbps+
Agile radioI/O
Software defined modem Network Processor
WINLAB’s “network centric” concept for cognitive radio prototype (..under development in collaboration with GA Tech & Lucent Bell Labs)
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Concluding Remarks
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Concluding Remarks: ORBIT TestbedOpen-access next-generation wireless network testbed being developed at Rutgers for NSF network research testbeds (NRT) programLarge scale “radio grid emulator” for evaluating new concepts for future wireless networks, e.g. ad-hoc networks, cognitive radio protocols, ...Also, outdoor “field trial network” with open-interface 3G & WLAN for real-world application work
Static radio node
Radio link emulation
ORBIT radio node
“Open”APIAccess Point(802.11b)
End-user devices
Ad-hoclink
3Gaccess
link
HighSpeed
Net
Firewall
MobilityServer
Wiredrouters
EmulatorMapping
“Open”API
3G BTS
Global InternetGlobal Internetns-2+ scripts
&code
downloads
ResearchUser of Testbed
1. Radio Grid for Lab Emulation 2. Field Trial Network
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Concluding Remarks: ORBIT Radio Grid
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ORBIT: Field Trial System
Lucent “Base Station Router”with IP interface
“Open API” 802.11a,b,gORBIT radio node
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Concluding RemarksFuture wireless networks need ~100-1000x increases in density and bit-rate of radios motivates better spectrum coordination methods
Spot shortages of spectrum will occur if present static allocation is continued significant improvement achieved with dynamic allocation
Cognitive radio technologies can be characterized in terms of the combination of hardware complexity and level of protocol coordination
Possible cognitive radio schemes includeAgile radio with interference avoidance
Spectrum etiquette protocols: spectrum server, CSCC..
Adaptive networks via ad-hoc collaboration
Early technical results now available for some of these methods, but very different complexity factors and market implications…
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Concluding RemarksFuture research areas in cognitive radio include:
New concepts and algorithms for agile radio and spectrum etiquette protocols
Architecture and design of adaptive wireless networks based on cognitive radios
Detailed evaluation of large-scale cognitive radio systems using alternative methods
Spectrum measurement and field validation of proposed methods
Cognitive radio hardware and software platforms
User-level field trials of emerging cognitive radios and related algorithms/protocols may also be useful to gain experience
Controlled testbed experiments comparing different co-existence methods
Large-scale “spectrum server” trial for 802.11x coordination
Experimental deployments in proposed US FCC cognitive radio band
Success with cognitive radio technologies should lead to major improvements in spectrum efficiency, performance and interoperability
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