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Transcript of 1 Architecture and Protocol Design for Cognitive Radio Networks* Microsoft CR Summit, Jun 2008...
1
Architecture and Protocol Design for Cognitive Radio Networks*
Microsoft CR Summit, Jun 2008
Rutgers, The State University of New Jerseywww.winlab.rutgers.edu
Contact: Professor D. [email protected] *Collaborative project with
Profs. Srini Seshan & Peter Steenkiste, CMUAnd Prof. Joe Evans, U Kansas
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Cognitive Radio: Problem ScopeSpectrumAllocation
Rules(static)
INTERNET
BTS
AuctionServer
(dynamic)
SpectrumCoordination
Server(dynamic)
AP
Ad-hocsensor cluster(low-power, high density)
Short-range infrastructuremode network
(e.g. WLAN)
Collaborative ad-hoc networksMAC/PHY adaptation
Wide-area infrastructuremode network (e.g. 802.16)
Dense deployment of wireless devices, both wide-area and short-range
Proliferation of multiple radio technologies, e.g. 802.11a,b,g, UWB, 802.16, 3G femto, 4G, ..
New cognitive radio devices with programmable PHY/MAC
Available options include: Agile radios (interference
avoidance) Dynamic centralized
allocation methods Distributed spectrum
coordination (etiquette) Collaborative ad-hoc
networks
Etiquette policy
SpectrumCoordination
protocols
Spectrum Coordinationprotocols
Dynamic frequencyprovisioning
Scope of CognitiveRadio Protocol Stack
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Broad 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
StaticAssignment
StaticAssignment
InternetSpectrumLeasing
InternetSpectrumLeasing
“cognitive radio”schemes
UWB,Spread
Spectrum
UWB,Spread
Spectrum
“Open Access”+ smart radios
Unlicensed band +simple coord protocols
Cognitive Radio: Design Space
Needs protocol support unified framework
called “CogNet”
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CogNet Protocol: Architectural Principles
Decentralized spectrum coordination as an integral part of protocol capabilities
“mutual observability” achieved via explicit exchange of spectrum information
Support for ad hoc network collaboration Beacons that enable network bootstrapping and discovery without infrastructure support
Adaptive selection of PHY, MAC, routing methods Control framework that enables on-the-fly selection of data path protocol components
Cross-layer control exchanged across protocol layers Access to cross-layer information necessary for cross-layer adaptation
Logical separation of control & data for flexible design and low overhead
Minimize contention between control & data (…>>50% overhead in 802.11 networks!)
Efficient integration with the wired Internet Aggregation of routing and cross-layer control information at boundary/gateway nodes
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“CogNet” Protocol Stack
Global Control Plane (GCP) Common framework for spectrum allocation, PHY/MAC bootstrap, topology
discovery and cross-layer routing
Data plane Dynamically linked spectrum mgmt, PHY, MAC, Network modules and
parameters as specified by control plane protocol
Control PHY
Control MAC
SpectrumMgmt
- BootstrapDiscovery
PHY
MAC
Network
Transport
Application
Control Plane Data Plane
Global Control Plane
Data Plane
Control API
Data Path
Establishment
Naming&
Addressing
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CogNet Protocol: Common Spectrum Coordination Channel (CSCC)
CSCC enables mutual observation between heterogeneous nodes to explicitly coordinate spectrum usage
CSCC function is an integral part of the CogNet global control plane (GCP)
• Exchange of CSCC messages by an extra narrow-band (low bit-rate) radio • Periodically broadcast spectrum usage parameters to neighbors• Enables distributed algorithms for spectrum co-existence
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CogNet Protocol: Packet Format
MessageType
Flags SourceAddress
IE length IE(1) IE(n)
1B 1B 6B 2B variable variable
Generic GCP Packet: 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). .
. . . Device Name and Description
IE length. . . MAC Address
Source MAC Address (cont). . .
0 8 16 24 31
Tx Pwr (8b) Rx Pwr (8b)
Example CSCC message used in WLAN-Bluetooth prototype at WINLAB
Message type Flags Source MAC Address
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CogNet Protocol: Validating GCP-based Spectrum Coordination on ORBIT
Multi-radio node 802.11a/b/g ad-hoc WiFi infrastructure mode (AP to
clients) Bluetooth
64kbps voice calls File synchronization between
PDAs, phones and laptops Mouse/keyboard
Zigbee Sensors
Potential WiMax Aggregated web/email traffic
to base stations
ORBIT Radio Grid
GCP Coordination Range
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CogNet Protocol: Validating GCP-based Spectrum Coordination on ORBIT (cont.)
Data Radio Service
PHY Type IEEE 802.11g(Atheros
AR5212)
Bluetooth(USB Dongle)
Frequency 2427-2447MHz 2402-2480MHz
Modulation OFDM (256 FFT) QAM
FHSS
Transmit Power
18dBm 4dBm (~10m) (class 2)20dBm (~100m) (class 1)
PHY Rate 1M-54Mbps AutoRate
Upto 1Mbps (class 2)Upto 4Mbps (class 1)
Data session Pareto ON/OFF variable rate CBR: 5 sec
random session
Constant audio streaming (64, 128,320,512,
1024kbps)
BT
WiFi
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CogNet Protocol: Validating GCP-based Spectrum Coordination on ORBIT (cont.)
Throughput Drops by ~3-4x in the case of 802.11g nodes and by ~1.5-2x for bluetooth nodes in dense topologies with 4 wifi and 4 Bt links. Results Averaged over 5 different topologies & load conditions. indicates the need for spectrum coordination
Wifi Performance
0.00
20.00
40.00
60.00
80.00
100.00
120.00
No-Interf With-Interf
Coexistence Effect on Wifi
Perc
en
tag
e T
hro
ug
hp
ut
802.11g Throughput
BT-Performance
0
20
40
60
80
100
120
No-Interf With-Interf
Coexistence Eff ect on BT
BT-Throughput
UDP throughput results with and without interference from other BT/WiFi users
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Characteristics : Each individiual in the room carries two
radios bluetooth and wifi Node density High
28 radios in ~3000sqft 14 Bluetooth radio 14 Wifi radio
1M 5M 10M 15M
-50
0
50
100
WiFi offered load (bps)BT load 1Mbps
Wifi (BT-Rate) Wifi (BT-BO) BT (BT-Rate) BT (BT-BO) Total (BT-Rate) Total (BT-BO)
Thr
ough
put I
mpr
ovem
ent (
%)
CogNet Protocol: Validating GCP-based Spectrum Coordination on ORBIT (cont.)
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CogNet Protocol: Beacon Format
Beacon format: (extended form of CSCC) Short message, low-layer function
Link weight/metric calculation: Estimate maximum supported data PHY rate
Direct link weight (proportional to achievable link rate)
M S G Type Flags S equenc e NumberS ourc e ...
...Identifier M ax P HY RateM ax T rans mit P ower B eac on T rans mit P ower
Num o f Reac h M AC Type M AC B us y Indic a to r
1 8 16 24 32
NA CF FD 0 0 0 0 0
8 10 12 14 16
Flags :
}),(min{},min{ maxmaxmaxmax jijmapjiij RSNRfRRR 0
)(
)(max Pr
NPt
PtSNR
Bji
Bjii
ij
},min{max MACjMACiijij RL MAC Idle Ratio
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CogNet Protocol: Network Discovery
Obtain global awareness by aggregating local link states Discover end-to-end paths with path weight Use only one-hop broadcast for periodical update Trade-off between network setup time and overhead
Link state aggregation message format Flags: PR – Poll (0) / Response (1), UB – Unicast (0) / Broadcast (1) response
required, FD – Forwarded or not, FU – Full or updated
MSG Type Flags Source......Identifier
TTL Valid Time Number of VectorsMessage Hash ID
Link S tate Vector 1
Link S tate Vector 2
. . . . . .
1 8 16 24 32
P R UB FD FU 0 0 0 09 10 11 12 13 14 15 16
F lags :
Destination Node......Identifier E2E P ath Weight
Next Hop Node......Identifier Hop Count
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CogNet Protocol: Data Path Establishment Hop-by-hop cross-layer parameter setup
Configure data plane and reserve radio resources by joint frequency/power/rate/bandwidth allocation
Unified message format for “up/down” hop setup
Multi-channel Data Path
Link State Aggregation
Control Plane Coverage
Link State Table
SourceDestination
Hop-by-hop Resource Allocation
M S G Type Flags M es s age S ender ...... Identifie r
Flow Des tina tion ...... Identifie r S es s ion Dura tion
C urrent T ime S tampHop R ec e ive r ...
... Identifie r M AC Type as S enderC hanne l Ava ilab ility M ap
M in P WR M ax P WR M in R a te M ax R a teHop S ender ...
... Identifie r M AC Type as R ec e ive rFrequenc y B andwidth
M odula tion C oding TX P ower P HY R a te
1 8 16 24 32
UC R V S D O T 0 0 0 09 10 11 12 13 14 15 16
F lags :
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CogNet Protocol: ns2 Simulation
Evaluation by ns-2 simulations Bootstrap/Discovery: network setup time, overhead, theoretical end-to-end rate DPE: joint F/P/R allocation success ratio, overhead Naming/addressing: uniqueness of IP/Name
Ad hoc network – nodes randomly boot up
Control Interface
(802.11b)
Data Interface
(generic OFDM radio parameters)
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CogNet Protocol: Discovery & Path Setup Simulation Results
Maximum and average network setup time (BSB interval 2sec, LSA interval 5sec, nodes randomly start [0, 4]sec)
Control overheadTheoretical max end-to-end rate averaged over the network
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CogNet Protocol: Dynamic MAC Switching Using GCP Control GCP offers control support necessary for MAC switching, for example from
CSMA to TDMA GCP messages carry state information needed by decentralized MAC
switching algorithm at each node GCP control used to set up TDMA schedule involving multiple nodes
Control link
Data path
Sender
Receiver
CH1_CSMA
CH2_CSMA
CH4_CSMA
CH3_CSMA
CH5_CSMA
CH1_CSMA
Delay increase > 20%Request TDMA SwitchA
B
CH10_TDMA Slot = 1
CH10_TDMA Slot = 3
CH10_TDMA Slot = 5
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CogNet Protocol: Dynamic MAC Switching Using GCP Control (cont.)
Sender Node A Node B Receiver
Preferred Channel List
Match channel
CH3_CSMA
Delay > 20%
Preferred Channel List
Match channel
CH5_CSMA Preferred Channel List
Match channel
CH1_CSMA
TDMA Join (Slot #3)TDMA Join (Slot #1)
TDMA Join (Slot #5)
CH10_TDMA (Slot #3)CH10_TDMA (Slot #1)
CH10_TDMA (Slot #5)
Request TDMA switchRequest TDMA switch
Request TDMA switch
GNU radio implementation currently in progress Sample protocol exchange between nodes shown below
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CogNet Protocol: Future Work
Complete validation of key components MAC switching, cross-layer routing protocols, adaptation algorithms, …
Complete baseline v1.0 protocol spec Support for dynamic spectrum, bootstrap/discovery, MAC switching and cross-
layer routing
End-to-end wired Internet integration issues CR supernode and aggregation gateway details
Protocol implementation on GNU radio platform GNU/ORBIT release planned for AY08-09 ORBIT upgrade to URSP2
Experiments with adaptive wireless networks Apply to dynamic networking scenarios (tactical, vehicular) and demonstrate value of
coordination, cooperation and adaptation
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Future work: ORBIT Node Upgrade to CR ORBIT radio grid testbed currently supports ~10 GNU radios and for ~100 low cost
programmable radio boards Plan to upgrade ~64 radio nodes with combination of GNU/USRP2 boards and WINLAB
hardware platforms for higher performance evaluations; will include baseline CogNet stack
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
ProgrammableORBIT radio node
URSP2CR board
Planned upgrade(2007-08)
Current ORBIT sandbox with GNU radio