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Pål GrønsundHai Ngoc PhamTelenor R&I
Simula Research Laboratory
03.04.09
SENDORA Project and Dynamic Spectrum Access in Primary OFDMA Systems
~85%
A cognitive radio implements a set of functions
SpectrumMobility
SpectrumSensing
SpectrumDecision
SpectrumSharing
TransmittedSignal
Primary UserDetection
DecisionRequest
ChannelCapacity
SpectrumHole
SpectrumCharacterizationRF
Stimuli
Radio Environment
PowerFrequency
Time
SpectrumHoles
Spectrum occupiedby licensed users
Secondary User
[Figures inspired by Akyildez. I, Milano’08][Animations by Gronsund, P’09]
4
This talk will be split into two main parts
Opportunities for Dynamic Spectrum Access in Primary OFDMA Systems
SENDORA Project Overview
SENDORA concept consists in studying and developing a "Sensor Network aided Cognitive Radio" technology
Primary Network
Cognitive Network
Wireless Sensor Network
queries on spectrum status
reports on spectrum status
Identify and analyze operational scenarios of the Wireless Sensor Network aided Cognitive Radio technology
Define and simulate WSN aided opportunistic access and dynamic resources allocation strategies for cognitive radios
Design a flexible and reconfigurable architecture, and demonstrate through a proof-of-concept the WSN aided Cognitive Radio technology
3 main project objectives are defined
WP1Project
Management
WP8Dissemination
WP2 Scenarios, System requirements and definition
WP7 System integration and Demonstration
WP3Sensing
WP4CognitiveActuation
WP5Cooperative
Communications
WP6WSN design
Work Package breakdown, and participants
Wireless broadband will be an important service for users and operators in the future
Most users are stationary when needing mobile broadband
Cognitive radio can offer high bit rates and low costs
Can later be extended towards mobility
The selected scenario is “Nomadic broadband in urban and suburban areas”
Fusion centre
InternetInternet
SS
C,SC,S
CC
A,S,CA,S,C
A,SA,SA,SA,S
SS
SS
CC
SS
Ad hoc network
Internet broadband access
Ad hoc broadband
Sensing information
Internet broadband access
Ad hoc broadband
Sensing information
S S
Primary Systems
Primary Systems
C = Centralized access capabilityS = Sensing capabilityA = Ad hoc capability
A centralized system architecture with a fusion centre is proposed
Dynamic Spectrum Access (DSA) will enable a secondary system to utilize available spectrum
DSA
PU (Primary User)SU (Secondary User)
Current Mobile WiMAX profiles uses OFDMA and TDD
TDD (Time Division Duplex)OFDMA (Orthogonal Frequency Division Multiple Access)
Scheduling determines how bursts are mapped onto the OFDMA frame
VerticalStriping
HorizontalStriping
RectangularScheduling
[figures from WiMAX Forum, ns-2 System Documentation]
FrameNum: 2410, Burst 4: start=3 (12.054552) numSubchanels=1 subchannelOffset=2 duration=3 :ULCID=3 UIUC=11FrameNum: 2410, Burst 5: start=3 (12.054552) numSubchanels=1 subchannelOffset=3 duration=3 :ULCID=1 UIUC=11FrameNum: 2410, Burst 6: start=15 (12.055923) numSubchanels=35 subchannelOffset=0 duration=0 :ULCID=-1 UIUC=14FrameNum: 2411, Burst 0: start=3 (12.056345) numSubchanels=29 subchannelOffset=0 duration=2 :DLCID=65535 DIUC=2FrameNum: 2411, Burst 1: start=5 (12.056573) numSubchanels=56 subchannelOffset=0 duration=4 :DLCID=16393 DIUC=7FrameNum: 2411, Burst 2: start=28 (12.059202) numSubchanels=30 subchannelOffset=0 duration=0 :DLCID=-1 DIUC=14FrameNum: 2411, Burst 0: start=0 (12.059209) numSubchanels=30 subchannelOffset=0 duration=2 :ULCID=-1 UIUC=1FrameNum: 2411, Burst 1: start=2 (12.059437) numSubchanels=30 subchannelOffset=0 duration=1 :ULCID=-1 UIUC=2FrameNum: 2411, Burst 2: start=3 (12.059552) numSubchanels=1 subchannelOffset=0 duration=3 :ULCID=5 UIUC=11FrameNum: 2411, Burst 3: start=3 (12.059552) numSubchanels=1 subchannelOffset=1 duration=3 :ULCID=4 UIUC=11FrameNum: 2411, Burst 4: start=3 (12.059552) numSubchanels=1 subchannelOffset=2 duration=3 :ULCID=1 UIUC=11FrameNum: 2411, Burst 5: start=15 (12.060923) numSubchanels=35 subchannelOffset=0 duration=0 :ULCID=-1 UIUC=14FrameNum: 2412, Burst 0: start=3 (12.061345) numSubchanels=29 subchannelOffset=0 duration=2 :DLCID=65535 DIUC=2FrameNum: 2412, Burst 1: start=5 (12.061573) numSubchanels=56 subchannelOffset=0 duration=4 :DLCID=16393 DIUC=7
Ns-2 source code can be modified to output relevant information
direction /Connection ID
symbol offset
subchannel offset
#subchannels #symbols
2 users, Downlink CBR traffic (1500 Bytes, 20 pps)
burstprofile
PU1DL
Initial Ranging
Available
Avail-able
Frame Index
PU3DL
PU2DL
Pre
am
ble
UL
MA
PD
L M
AP PU1 UL
PU2 UL CAPtot
OFDMA Capacity(Subch * Symb)
Frequency(Subchannels)
Time(Symbols)
CAPavail
CAPused
Available capacity can be calculated
OFDMA Frame
Downlink CBR traffic (1500 bytes, 20 pps) for 20 users (Best Effort)
BW: 10 MHzDL-UL ratio: 2/3-1/3
47.56 % Occupancy
OF
DM
A C
ap
ac
ity
Frame Index
OF
DM
A C
ap
ac
ity
Frame Index
DL : Max OFDMA Capacity 850 (30*28) UL : Max OFDMA Capacity 525 (35*15)
BW: 10 MHzDL-UL ratio: 2/3-1/3
Uplink CBR traffic (1500 bytes, 20 pps) for 20 users (Best Effort)
95.97 % Occupancy
OF
DM
A C
ap
ac
ity
Frame Index
DL : Max OFDMA Capacity 850 (30*28) UL : Max OFDMA Capacity 525 (35*15)
OF
DM
A C
ap
ac
ity
Frame Index
Temperature plot for occupancy for all OFDMA frames indicate potential for DSA
Downlink CBR traffic for 20 BE users (20 seconds)
Occupancy distribution over all the traffic indicates potential for DSA
Downlink CBR traffic for 20 BE users (20 seconds)
OFDM Symbols
Pro
ba
bil
ity
of
Oc
cu
pa
nc
y
Subchannels
CBR traffic for 20 BE users (1 sec)
UplinkDownlink
UL
Ca
pac
ity
(S
ub
Ch
*Sy
mb
)
Frame Index
The consecutiveness of occupancy on a frame-by-frame basis is important for DSA
Frame Index
DL
Ca
pac
ity
(S
ub
Ch
*Sy
mb
)
DL Subframe, DL CBR traffic for 20 BE users (500 ms)
One approach is to derive schemes for probability of occupancy (eg. time dependent occupancy distribution)
Frame IndexSlot Index
Pro
ba
bil
ity
of
Oc
cu
pa
nc
y
Capacity, distributions and consecutiveness of available OFDMA spectrum is characterized
Derivation of schemes, protocols and systems for DSA in primary OFDMA systems is necessary
Questions?Pal Gronsund ([email protected])
Hai Gnoc Pham ([email protected])
In summary, we are characterizing the opportunities for DSA in primary OFDMA systems
DSA