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

Vertical striping is used to allocate OFDMA slots in the WiMAX ns-2 simulator

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 (pal.gronsund@telenor.com)

Hai Gnoc Pham (hainp@ifi.uio.no)

In summary, we are characterizing the opportunities for DSA in primary OFDMA systems

DSA