Cognitive radio networks allow secondary users to opportunistically access unused spectrum licensed to primary users. Primary user emulation (PUE) attacks involve malicious users mimicking primary user signals to prevent secondary usage. This document discusses three methods for detecting PUE attacks: energy detection measures signal power levels; cyclostationary feature detection analyzes periodic signal properties; and localization verifies positions based on signal strength. A proper cognitive radio architecture is needed for secondary users and base stations to collaborate on PUE detection using a combination of these methods.

1. Detecting PUE attacks in Cognitive Radio Networks
Research Methods
Fan Jin
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2. Cognitive Radio
Existing frequency resources are almost allocated by
companies or organizations
Utilization of frequency resources are unbalanced
Cognitive Radio can improve the efficiency of
utilizing existing frequency resources
Simple Example:
Mobile phone user can use TV signal to talk or SMS

3. Some Concepts
Primary user: user who has paid for a specific band
Secondary user: user who has not paid for a
frequency, but wants to use a frequency for
communication
White space, hole or fallow band: in a specific time
frame, a primary user is not using his paid frequency
channel
Hand-off: when primary user comes to use his
frequency, secondary users have to quit and look for
another white space

4. Primary User Emulation
Attack
Malicious users mimic primary user’s signal
Other secondary users believe the primary user is still
in, hence they are unable to use the fallow band
Selfish PUE attacker and Malicious PUE attacker
Impact of PUE attacks

5. PUE attack detection
Secondary user needs to correctly identify primary
user’s signal
No modification should be applied to primary user
Three research methods: Energy detection,
Cyclostationary feature detection and Localization

6. a radio signal should
look like…

7. a real TV signal …

8. Energy Detection
Energy detector measures the energy in the input
wave over a specific time interval.
Measures the power level of the received signal at
the secondary user receiver and compare it with the
signal from real primary user
A threshold is required for identification
Advantage: Former knowledge of the primary user
signal characteristic (much more than the energy
level) is not required.
Disadvantage: path loss, path fading

9. Cyclostationary Feature
Detection
Utilizes the cyclic feature of a signal to detect it
If the amplitude is periodic and there exists a peak
value for each period, the value is compared to a
predetermined threshold
Cyclic autocorrelation function (CAF) and Cyclic
spectrum density (CSD)
Advantage: robust against noise with unknown
variance
Disadvantage: computational complexity and long
observation time

10. Localization
Non-interactive localization scheme is required
Location Verification scheme: ratio of distance and
energy level
Localization scheme:
 Received Signal Strength (RSS) based localization
 Triangulation

11. RSS based localization scheme

12. Conclusion
A proper architecture is required, contains primary users,
secondary users and secondary user base stations:
Secondary users will need to communicate each
other or with base stations for exchanging
messages and updating final results
A combination of above methods need to be used to
successfully detect PUE attacks
Other techniques such as machine learning or data
smoothing may be used to increase the accuracy of final
decision

13. Questions?