Transcript Slide 1

SENDORA Project and Dynamic Spectrum Access in
Primary OFDMA Systems
Pål Grønsund
Hai Ngoc Pham
Telenor R&I
Simula Research Laboratory
03.04.09
~85%
A cognitive radio implements a set of functions
Frequency
Power
Spectrum
Holes
Time
Spectrum occupied
by licensed users
Secondary User
Transmitted
Signal
Spectrum
Mobility
Spectrum
Sharing
Radio
Environment
RF
Stimuli
Primary User
Detection
Decision
Request
Channel
Capacity
Spectrum
Characterization
Spectrum
Sensing
Spectrum
Hole
Spectrum
Decision
[Figures inspired by Akyildez. I, Milano’08]
[Animations by Gronsund, P’09]
This talk will be split into two main parts
SENDORA Project Overview
Opportunities for Dynamic Spectrum
Access in Primary OFDMA Systems
4
SENDORA concept consists in studying and developing a
"Sensor Network aided Cognitive Radio" technology
Primary Network
Cognitive Network
queries on
spectrum
status
Wireless
Sensor
Network
reports on
spectrum
status
3 main project objectives are defined
 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
Work Package breakdown, and participants
WP2 Scenarios, System requirements and definition
WP5
Cooperative
Communications
WP1
WP3
Project
Management
Sensing
WP4
Cognitive
Actuation
WP8
Dissemination
WP6
WSN design
WP7 System integration and Demonstration
The selected scenario is “Nomadic broadband in urban and
suburban areas”
 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
A centralized system architecture with a fusion centre is
proposed
Primary
System
s
C = Centralized access capability
S = Sensing capability
A = Ad hoc capability
Dynamic Spectrum Access (DSA) will enable a secondary
system to utilize available spectrum
PU (Primary User)
SU (Secondary User)
DSA
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
Vertical
Striping
Rectangular
Scheduling
Horizontal
Striping
[figures from WiMAX Forum, ns-2 System Documentation]
Ns-2 source code can be modified to output
relevant information
subchannel
offset
symbol
offset
#subchannels
direction /
Connection ID
#symbols
burst
profile
FrameNum: 2410, Burst 4: start=3 (12.054552) numSubchanels=1 subchannelOffset=2 duration=3 :ULCID=3 UIUC=11
FrameNum: 2410, Burst 5: start=3 (12.054552) numSubchanels=1 subchannelOffset=3 duration=3 :ULCID=1 UIUC=11
FrameNum: 2410, Burst 6: start=15 (12.055923) numSubchanels=35 subchannelOffset=0 duration=0 :ULCID=-1 UIUC=14
FrameNum: 2411, Burst 0: start=3 (12.056345) numSubchanels=29 subchannelOffset=0 duration=2 :DLCID=65535 DIUC=2
FrameNum: 2411, Burst 1: start=5 (12.056573) numSubchanels=56 subchannelOffset=0 duration=4 :DLCID=16393 DIUC=7
FrameNum: 2411, Burst 2: start=28 (12.059202) numSubchanels=30 subchannelOffset=0 duration=0 :DLCID=-1 DIUC=14
FrameNum: 2411, Burst 0: start=0 (12.059209) numSubchanels=30 subchannelOffset=0 duration=2 :ULCID=-1 UIUC=1
FrameNum: 2411, Burst 1: start=2 (12.059437) numSubchanels=30 subchannelOffset=0 duration=1 :ULCID=-1 UIUC=2
FrameNum: 2411, Burst 2: start=3 (12.059552) numSubchanels=1 subchannelOffset=0 duration=3 :ULCID=5 UIUC=11
FrameNum: 2411, Burst 3: start=3 (12.059552) numSubchanels=1 subchannelOffset=1 duration=3 :ULCID=4 UIUC=11
FrameNum: 2411, Burst 4: start=3 (12.059552) numSubchanels=1 subchannelOffset=2 duration=3 :ULCID=1 UIUC=11
FrameNum: 2411, Burst 5: start=15 (12.060923) numSubchanels=35 subchannelOffset=0 duration=0 :ULCID=-1 UIUC=14
FrameNum: 2412, Burst 0: start=3 (12.061345) numSubchanels=29 subchannelOffset=0 duration=2 :DLCID=65535 DIUC=2
FrameNum: 2412, Burst 1: start=5 (12.061573) numSubchanels=56 subchannelOffset=0 duration=4 :DLCID=16393 DIUC=7
2 users, Downlink CBR traffic (1500 Bytes, 20 pps)
Vertical striping is used to allocate OFDMA
slots in the WiMAX ns-2 simulator
Available capacity can be calculated
Preamble
DL MAP
UL MAP
Frequency
(Subchannels)
OFDMA Capacity
(Subch * Symb)
PU1 UL
PU1
DL
Available
PU2
DL
OFDMA Frame
PU3
DL
CAPtot
PU2 UL
CAPavail
Available
Initial Ranging
Time
(Symbols)
CAPused
Frame Index
Downlink CBR traffic (1500 bytes, 20 pps) for 20
users (Best Effort)
BW: 10 MHz
DL-UL ratio: 2/3-1/3
OFDMA Capacity
OFDMA Capacity
47.56 % Occupancy
Frame Index
DL : Max OFDMA Capacity 850 (30*28)
Frame Index
UL : Max OFDMA Capacity 525 (35*15)
Uplink CBR traffic (1500 bytes, 20 pps) for 20
users (Best Effort)
BW: 10 MHz
DL-UL ratio: 2/3-1/3
OFDMA Capacity
OFDMA Capacity
95.97 % Occupancy
Frame Index
DL : Max OFDMA Capacity 850 (30*28)
Frame Index
UL : Max OFDMA Capacity 525 (35*15)
Temperature plot for occupancy for all OFDMA
frames indicate potential for DSA
Downlink CBR traffic for 20 BE users (20 seconds)
Probability of Occupancy
Occupancy distribution over all the traffic
indicates potential for DSA
Sub
channels
OFDM Symbols
Downlink CBR traffic for 20 BE users (20 seconds)
DL Capacity (SubCh*Symb)
UL Capacity (SubCh*Symb)
The consecutiveness of occupancy on a
frame-by-frame basis is important for DSA
Frame Index
Frame Index
Downlink
Uplink
CBR traffic for 20 BE users (1 sec)
Probability of Occupancy
One approach is to derive schemes for probability of
occupancy (eg. time dependent occupancy distribution)
Slot Index
Frame
Index
DL Subframe, DL CBR traffic for 20 BE users (500 ms)
In summary, we are characterizing the opportunities for
DSA in primary OFDMA systems
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])
DSA