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, 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 λ max λ min = σ n 2

Maximum-Minimum Eigen Value Detection (MMEVD) Recieved Signal r(t) Upon predefined threshold γ of the ratio λ max / λ min 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

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 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

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