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224B: Fundamentals of Wireless Communications

Professor David Tse

Experimental Study of Energy Detection

and Cooperation for Cognitive Radios

Artem TkachenkoStela Llusha

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Agenda

1. Introduction

2. Theoretical Background 3. Experimental Setup

4. Experimental Results5. Future Work

6. Questions

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INTRODUCTION

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FCC Spectrum Allocation

Spectrum is scarce

Frequencies below 3

GHz has been fullyallocated

Multiple allocations in

a same band

Low and inefficient spectrum utilization

Cognitive Radios have been proposed toimprove spectrum utilization

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Cognitive Radios

Two types of Cognitive Radio schemes:

1. Primary Receiver Detectors

Mainly in indoor environment2. Primary Transmitter Detectors

Indoor and outdoor environments

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Project Goals

Experimental analysis of the following issues ofdetecting Primary Rx using energy detection:SNR wallShow that under noise uncertainty, detection for a

single secondary user is impossible at sufficientlylow SNRCooperationShow that cooperation among cognitive radios canimprove the probability of detection, as a functionof the number of radios and their spatial separation.

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THEORETICAL BACKGROUND

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Energy DetectorsBinary Hypothesis Testing:

H 0 : Y[n] = W[n] n = 1,.,NH

1 : Y[n] = X[n] + W[n] n = 1,.,NEnergy Detector Test Statistics:

T (Y) =[ ]

0

11

0

2

H

H N

n

nY