Maximum-Minimum Eigen Value Based Spectrum Scanner

Mohamed Hamid and Niclas Björsell

Center for RF measurement Technology, University of Gävle, Sweden

Communications Systems Lab, Royal Institute of Technology, Stockholm, Sweden

@RFMTC 2011, Gävle, October, 2011

Outlines

• Introduction

• Spectrum Detection Techniques

• Maximum-Minimum Eigen Value Detection

(MMEVD)

• Rectangular Filtering for sub-bands spectrum

scanning with MMEVD

• Measurements Results

• Conclusions

Introduction

• Current spectrum regulation policy relies on Static spectrum access

•Wireless services and technologies are growing rapidly Lack of radio resources

•Radio Spectrum is under-utilized

•Dynamic Spectrum access (DSA) policy

Introduction(Cont.)

• What is the spectrum opportuinty?! A free of use channel (band) subject to the recieved power in a specific time at a specific location

•How to find a spectrum Opportuity •Spectrum Sensing and/or •Geolocation Databse•Beacon based Spectrum Opportunities

Spectrum Detection Techniques

•Energy Detector

Requires a prior knowledge of the system background noise

•Matched Filtering•Auto-correlation Detection

Require a prior knowledge of the primary system signal

•Maximum-Minimum Eigen Value Detection

Maximum-Minimum Eigen Value Detection (MMEVD)

•Signal frequency components α Eigen values of the auto correlation Matrix of the signal

λmax

λmin = σn2

Maximum-Minimum Eigen Value Detection (MMEVD)

•Recieved Signal r(t)

•Upon predefined threshold γ of the ratio λmax/ λmin the decission is made if it is a signal or just noise

•MMEVD tests the extent of the flatness of the spectrum • Filtering is a problimatic when scanning for sub-bands is to take place

http://www.hig.se/

Rectangular Filtering for sub-bands spectrum scanning with MMEVD

Solution:

Rectangular Filtering , i.e. talking the spectrum lines lie inside the sub-band of interest and throw away the rest

Time Domain Signals

Do MMEVD

Measurements Results

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

SNR

p fa

MMEVD

ED

• Measured BW : 10 MHz• # Sub-channels: 5 (2MHz each)

Conclusions

• Sub-bands spectrum scanning is feasible with rectangular filtering and MMEVD

• MMEVD introduces probability of false alarm much less than the one introduced by Energy Detection

THANKS FOR YOUR ATTENTION

QUESTIONS AND COMMENTS ARE WELCOME