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Overcoming the Sensing-Throughput

Tradeoff in Cognitive Radio Networks

S.Stotas, A.Nallanathan

ICC 2010

Mar.3 2011

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Outline

Introduction

Novel Cognitive Radio System

Throughput of the Proposed System Throughput of the Proposed System under the

Energy Detection Scheme

Simulation Results

Conclusions

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Introduction

The conventional frame structure exists a tradeoff

between sensing duration and data transmission

duration Its impossible to maximize throughput and sensing

capabilities at the same time

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Novel Cognitive Radio System

i)Novel Frame Structure

Advantages:

1.Increase sensing time better Pd and Pf

2.Decrease harmful interference and improve spectrumutilization

3.Continuity of data transmission

4.Improve throughput

5.Can use more complex sensing techniques(cyclostationary) 4

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Novel Cognitive Radio System

ii) Novel Cognitive Receiver Structure The received signal at the secondary user is

:the actual status of frequency band

sp:the received signal from primary users

hs:the channel between the secondary transmitter and the secondary receiver

xs:the signal from the secondary transmitter

n:the additive noise

The remaining signal

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Throughput of the Proposed System

Define two cases:

(i)A frequency band is correctly detected to be idle

(ii)A frequency band is falsely detected to be idle

The throughput of the cognitive radio network in

above two cases are denoted R0 and R1 respectively

Notations:

T:frame duration

:sensing time

P(H0):P{the frequency band is idle}

P(H1): P{the frequency band is active}

:target probability of detection

dP

dP

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The average achievable throughput with the

conventional frame structure is

where

The average achievable throughput of the novel

system is

and

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For a target detection probability

Namely

for0 < T

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Throughput of the Proposed System

under the Energy Detection Scheme

The test statistic for the energy detection is

yr:the received signal at the secondary user

M:the number of samples

For a complex-valued PSK signal and CSCG noise

and the false alarm for given target detection prob.

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Similar to the previous

Finally

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Fig 4. and fig 5. show that the novel system hasbetter false alarm and throughput performance than

the conventional frame structure

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Either the target detection prob. Increases or thetarget SNRp decreases, the achievable throughput of

novel system is better

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Conclusions

The proposed cognitive radio system exhibits

improved throughput and sensing capabilities

compared to the conventional system

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