Cognitive Radio

Company LOGO

Cognitive Radio

Principles

Hyewon Lee M.S. Candidate

Multimedia & Wireless Networking Lab. Seoul National University

Contents

Cognitive Radio

Reference survey paper

Cognitive Networks

Concluding Remark

1

2

3

4

Cognitive Radio

‹ Motivation: Spectrum Scarcity

Cognitive Radio

‹ Cognition (Noun):

„ Cognition is the mental process involved in knowing, learning,

and understanding things.

- Collins Cobuild Dictionary

‹ Cognitive Radio

„ Cognitive Radio is an intelligent wireless communication

system that is aware of its surrounding environment and uses the methodology of understanding-by-building to learn from the environment and adapt its internal states to statistical

variations in the incoming RF stimuli by making corresponding changes in certain operating parameters in real-time.

Cognitive Radio

‹ Cognitive Radio

„ Cognitive radio is a paradigm for wireless communication in

which either a network or a wireless node changes its transmission or reception parameters to communicate

efficiently avoiding interference with licensed or unlicensed users. This alteration of parameters is based on the active

monitoring of several factors in the external and internal radio environment, such as radio frequency spectrum, user behavior and network state.

Spectrum access policy

Open

Spectrum

Spectrum

Trading

Fixed

Spectrum

Terminology

‹ Capability of cognitive radio

„ Every possible parameter observable is taken into account „ Spectrum sensing cognitive radio

„ Only radio frequency band is taken into account

‹ Licenses of spectrum band

„ Primary network (user) „ Secondary network (user) „ Unlicensed band cognitive radio

Cognitive Radio

‹ Basic cognitive cycle

•Ref.: S. Haykin, “Cognitive Radio,” JSAC 2005 •Estimation of interference temperature of the radio environment

•Detection of spectrum holes

•Estimation of channel-state information •Prediction of channel capacity for use by the transmitter

Cognitive Radio

‹ Main functions

„ Detecting unused spectrum „ Spectrum management

„ Capturing the best available spectrum „ Spectrum mobility

„ Maintaining seamless communication during the spectrum

transition

„ Spectrum sharing

„ Providing fair spectrum scheduling method

•Ref.: Ian F. Akyildiz, et al., “NeXt generation/dynamic spectrum access/cognitive radio wireless networks: A survey,” ComNet 2006

Cognitive Radio – Main functions

‹ Spectrum sensing

„ Detecting unused spectrum „ Non-cooperative detection

„ Energy detection

„ Matched filter detection

„ Cyclostationary feature detection „ Cooperative detection

„ Cooperation with

„ Primary network „ Secondary users

Interference Temperature

‹ Transmission power control

„ Receiver-centric

‹ Interference temperature

„ Real-time interaction between transmitter and receiver in

Interference Temperature

‹ Limitations of interference temperature model

„ Transmission power of secondary users „ Number of secondary users

„ Coordination with primary network „ Interference level of primary users „ Location information of primary users

Cognitive Radio – Main functions

‹ Spectrum management

„ Capturing the best available spectrum „ Spectrum analysis

„ Interference/Path loss „ Link errors/delay

„ Channel holding time „ Spectrum decision

„ Decision model

Cognitive Radio – Main functions

‹ Spectrum mobility

„ Maintaining seamless communication during the spectrum

transition

Cognitive Radio – Main functions

‹ Spectrum sharing

„ Spectrum sensing Æ spectrum allocation Æ spectrum access Æ

transmitter-receiver handshaking Æ spectrum mobility

„ Spectrum sharing architecture „ Centralized vs. Distributed „ Spectrum allocation behavior

„ Cooperative vs. Non-cooperative „ Spectrum access technique

„ Overlay vs. Underlay „ Rendezvous problem

SDR

‹ Software Defined Radio (SDR)

„ A technology that enables “reconfigurable system” for wireless

networks.

„ SDR builds up ‘multimode, multiband’ wireless device.

‹ SDR and Cognitive Radio

„ Cognitive radio is the ‘intelligence’ that sits above the SDR and

lets a SDR determine which mode of operation and parameters to use.

Cognitive Networks

‹ Cognitive Networks (DySpan 2005, MobiCom 2007)

„ Perceive current network conditions

„ Plan, decide, and act on such conditions „ Learn and adapt for future decisions

„ Takes into account end-to-end goals

„ Comparison between Cognitive Networks and Cognitive Radios „ End-to-end vs. point-to-point

Cognitive Networks

‹ Cognitive Network Framework

Cognitive ElementCognitive ElementCognitive Element End-to-end Goal

Cognitive Specification Language End-to-end

Goal End-to-endGoal

Software Adaptable Network API

Network

Status Sensors ConfigurableElementsConfigurable Elements Requirements Layer Cognitive Process Software Adaptable Network

Cognitive Networks

‹ Cognitive Specification Language

„ Translates end-to-end goal into local goals of cognitive elements

‹ Cognitive Elements

„ Run algorithms that reason, learn, and plan „ Actuate configurable elements

‹ Degree of Control

„ Full control vs. partial control „ Complexity

Concluding Remark

‹ Challenges

‹ Questions

References

‹ Ian F. Akyildiz, et al., “NeXt generation/dynamic spectrum

access/cognitive radio wireless networks: A survey,” ComNet 2006

‹ S. Haykin, “Cognitive Radio,” JSAC 2005

‹ Online link: http://en.wikipedia.org/wiki/Cognitive_radio ‹ Ryan W. Thomas, “Cognitive Networks,” DySPAN 2005