cognitive radio networks and their applications · fcc definition of cr • an intelligent wireless...

COIE Symbosium - 11 April 2019

Cognitive Radio Networks and their Applications

Prof. Dr. Hikmat N. Abdullah

[email protected]

1

Outline

• Motivation

• Software Defined Radio + Cognitive Radio

• Cycle of Cognitive Radio (Trends)

• Advantages and Applications of CR

• CR Enabling Techniques (Trends)

• Spectrum Sensing (Trends)

• Challenges and Research Issues

• Standardization

COIE Symbosium - 11 April 2019 2

Motivation

• Going wireless more and more...

• Lack of interoperability between different technologies

• Lack of spectrum (???)

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Spectrum Facts

Fixed Spectrum Assigment

Bandwidth is expensive and good

frequencies are taken

Recent measurements by the FCC in

the US show 70% of the allocated

spectrum is not utilized

Time scale of the spectrum occupancy

varies from msecs to hours

• More clever radio

• Frequency Agility----SPECTRUM SHARING

SOLUTION


Solution

Joseph Mitola 1992 Software Defined Radio (SDR)

radio primarily defined in software, which

supports a broad range of frequencies, and

its initial configurations can be modified

for user requirements.

Joseph Mitola 1999Cognitive Radio (CR)

SDR + Intelligence


CR Terminology!

The term Cognitive Radio was first suggested by

Prof. Joseph Mitola 1999

“The key feature of a Cognitive Radio is its ability to recognize the unused parts of

spectrum that is licensed to a primary user and adapt its communication strategy to

use these parts while minimizing the interference that it generates to the primary

user”


Primary and Secondary Users

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Spectrum hole

• A spectrum hole is a band of frequencies assigned to aprimary user, but, at a particular time and specific geographiclocation, the band is not being utilized by that user.


FCC Definition of CR

• An intelligent wireless communication system that is aware of itssurrounding environment, and uses the methodology ofunderstanding-by-building to learn from the environment andadapt its internal states to statistical variations in the incoming RFand making changes in certain operating parameters (e.g.,transmit-power, carrier frequency, and modulation strategy) inreal-time, with two primary objectives in mind:

• highly reliable communications whenever and wherever needed;

• efficient utilization of the radio spectrum.


The cycle of cognitive radio

• Spectrum Sensing

• Spectrum Management

• Spectrum Mobility

• Spectrum Sharing


How Cognitive Radio Works


Level Capability Comments

0 Pre-programmed A software radio

1 Goal DrivenChooses Waveform According to Goal. Requires

Environment Awareness.

2 Context Awareness Knowledge of What the User is Trying to Do

3 Radio AwareKnowledge of Radio and Network Components,

Environment Models

4 Capable of PlanningAnalyze Situation (Level 2& 3) to Determine Goals (QoS,

power), Follows Prescribed Plans

5 Conducts Negotiations Settle on a Plan with Another Radio

6 Learns Environment Autonomously Determines Structure of Environment

7 Adapts Plans Generates New Goals

8 Adapts Protocols Proposes and Negotiates New Protocols

Levels of Cognitive Radio Functionality


NormalUrgent

Level0 SDR1 Goal Driven2 Context Aware3 Radio Aware4 Planning5 Negotiating6 Learns Environment7 Adapts Plans8 Adapts Protocols

Allocate Resources

Initiate Processes

OrientInfer from Context

Parse Stimuli

Pre-processSelect Alternate

Goals

Establish Priority

PlanNormal

Negotiate

Immediate

LearnNew

States

Negotiate Protocols

Generate Alternate

Goals

Observe

Outside

World

Decide

Act

User Driven

(Buttons)Autonomous Determine “Best”

Plan

Infer from Radio Model

States

Determine “Best”

Known WaveformGenerate “Best”

Waveform

Trends for Cognitive Radio Cycle

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intelligence at all the 7 layers of the “OSI” model.

CR uses intelligent signal processing (ISP) at the physical layer of a wireless system and is achieved by combining ISP with software defined radio (SDR)


CR Network improves ACCESSIBILITYaccess various networks and services


CR Network improve ADAPTABILITYWhen user roams across borders, the device performs self-

adjustment to stay in submission with local radio operations and emissions regulations.


CR Network improves INTERCONNECTIVITY multi-terminal / multi-frequency communication devices.


CR Network improve SCALABILITYThe network can potentially scale to large numbers of users


CR Network improves RELIABILITY

self-configuring mesh wireless networks avoid failure by re-routing around node failures or congestion areas


Cognitive Radios vs. Conventional Radios

Conventional • operating in interference-free spectrum

• Unable to dynamically change parameters,channels or spectrum bands in response tointerference

• View congested radio spectrum as essentiallyunusable for communications due to heavyinterference

Cognitive• function in challenging conditions

• quickly identify unused “gaps” in spectrum

that are not being used

• find and tune to other spectrum ifinterference is detected on the frequenciesbeing used (example - xMax samples,detects and determines if interference hasreached unacceptable levels up to 33 timesa second)


Cognitive Radios vs. Conventional Radios


Applications of cognitive radio


Enabling Techniques for CR Communication


Exploitation Techniques

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• They may be used for communications by a secondary transmitter

and a secondary receiver.

• The goal is to decide between the two hypotheses, namely

X(t)=

N(t)

S(t)+N(t)

H0

H1

Spectrum Sensing

Optimization Parameters

• Detection probability

• False alarm probability

• Sensing Time

• Signal –to-Noise Ratio

• Energy Consumption

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Spectrum Sensing Technique

Non- cooperative scenario Cooperative scenario

Centralized DistributedRelay-

Assisted

Energy

detectionMatched filter

Cyclostationary

Spectrum Sensing Techniques


Non-cooperative Scenario Centralized Cooperative Scenario

PU Fading Effect

PU

FCFC

Fading Effect

FC

Sensing Stage

Transmission Stage

Transmission Stage

Spectrum Sensing Techniques


Trends in Spectrum Sensing

5G Techniques


Fusion Rules

Hard Fusion Rules

i. OR Rule

ii. AND Rule

iii. MAJORITY Rule

Soft Fusion Rules

i. Square Law Combination (SLC):

ii. Maximum Ratio Combination (MRC):

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Challenges and Research Issues

• Hardware • Learning Mechanisms• Cooperation-Processing Trade-off• Developing spectrum sharing behaviors• Sensitive detection• frequency assignment negotiation• Resource allocation• Security (Unintentional config..)• Integration with “spectrum market”


CR ANTENNAS

“ Sensing antenna” Wide band antenna which Continuously monitors The

frequency spectrum for activity

“ Reconfigurable antenna” narrow-band antenna which dynamically tune to aspecific range within the frequency spectrum to perform data transfer


Standardization efforts

• IEEE 802.22 WRAN (2004 )

• IEEE 1900–SCC41-DYSPAN (2010)

• SDR Forum (2008 )

• GNU Radio Project (2008 )

• DARPA xG (ITU-R) (2009 )

• JTRS (IMT-2000) (2011 )



• IEEE created the 802.22 Working Group (WG) for WRANs in November, 2004.

• This WG is assigned to develop an air interface (i.e., PHY and MAC) based on CRs for unlicensed

operation in the TV broadcast bands

• The focus of 802.22 is on rural broadband wireless access

• North America, the frequency band of operation of the IEEE 802.22 networks is 54–862 MHz

• the standard shall accommodate various international TV channel bandwidths of 6, 7, and 8 MHz

• The base station also coordinates “distributed sensing,” and controls the consumer equipments (CEs).

• The base station directs the CEs to measure different TV channels and provide feedback

• For an average spectral efficiency of 3 bits/s/Hz in the IEEE 802.22 systems, considering 12 users, the

minimum peak throughput rate is 1.5 Mbps per CE in the downstream direction and 384 kbps in the

upstream direction.

• The base station coverage range, which can be up to 100 km if transmission power is not an issue

(current specified coverage range is 33 km at 4 W).

IEEE 802.22 WRAN

34/37 NETLAB Seminar 7 March 2007

• Optimize transmission

parameters

• Adapt rates through feedback

• Negotiate or opportunistically

use resources

Physical Layer

MAC Layer

Network Layer

Transport Layer

Application Layer

OFDM transmission

Spectrum monitoring

Dynamic frequency selection,

modulation, power control

Analog impairments compensation

Routing, System Management, QoS and other upper layer issues...

Cross-layer design


• In 2010, the IEEE SCC41 is divided into four WGs termed as 1900.x, “x” being the WG.

• IEEE P1900.1 (Terminology and Concepts for Next Generation Radio Systems and Spectrum

Management):

• IEEE P1900.2 (Recommended Practice for Interference and Coexistence Analysis):

• IEEE P1900.3 (Dependability and Evaluation of Regulatory Compliance for Radio Systems with DSA):

• IEEE P1900.4 (Architectural Building Blocks Enabling Network-Device Distributed Decision Making for

Optimized Radio Resource Usage in Heterogeneous Wireless Access Networks):

• IEEE P1900.5: (Addressing the policy language issues)

• IEEE P1900.6: (Addressing RF sensing functions that can be managed in a terminal reconfiguration

manager)

• IEEE P1900.7 (Radio Interface for White Space DSA Radio Systems Supporting Fixed and Mobile

Operation):

• The IEEE SCC41 cooperate with the FCC (Federal Communications Commission), OFCOM UK, SDR

Forum, and OMG forum, and others.

IEEE Standard Coordinating Committee 41 (SCC41)


ETSI standardization

In October 2009, ETSI’s Technical Committee on Reconfigurable Radio Systems (RRS)

System Aspect Studies (WG1):

Reconfigurable Radio Equipment Studies (WG2):

Cognitive Network Management Studies (WG3):

Public Safety Studies (WG4):

International Telecommunication Union standardization

The International Telecommunication Union (ITU)-Radio communication sector (ITU-R) study Group 8

(Mobile, Radio Determination, Amateur and Related Satellite Services) deals with standardization of CRNs.

Application of SDR in International Mobile Telecommunications-2000 (3G mobile system provide access to a

wide range of telecommunication services)

The SDR technology is employed in the base station and the controllers of a mobile radio access network to

increase the flexibility of radio access networks.

THANKS


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