SENSING-THROUGHPUT TRADEOFF FORCOGNITIVE RADIO NETWORKS

GROUP MEMBERS

•M. Sarmad Hafeez•Jawad Ahmed

•Ahmed Shafqat•M. Ihsan Ul Haq

ABSTRACT Probability of detection and probability of false alarm. The

higher the probability of detection, the better the primary users are protected. However, from the secondary users’ perspective, the lower the probability of false alarm, the more chances the channel can be reused when it is available, thus the higher the achievable throughput for the secondary network.

Work divisionSection II presents

the general model for spectrum sensing and reviews the

energy detection scheme. The relation between probability of

detection and probability of false alarm is also established in

this section. In Section III, we study the sensing-throughput

tradeoff problem, and prove the existence of optimal sensing

time based on energy detection scheme. Section IV studies the

sensing scheme based on multiple mini-slots which achieves

time diversity. Distributed spectrum sensing using multiple

secondary users is studied in Section V. Performance evaluation and comparisons are given in Section VI, and finally,

conclusions are drawn in Section VII.

I. INTRODUCTION

INTRODUCTIONCognitive radio network that employs opportunistic spectrum access.In order to efficiently exploit the unused spectrum and effectively

protect the quality of service of licensed networks. For this reason, a time slot has been allocated for spectrum sensing at the beginning of each frame in the systems proposed so far.

During this slot, data transmission is prohibited, which results in the sensing throughput tradeoff problem.

Thus there could exist a fundamental tradeoff between sensing capability and achievable throughput for the secondary network.

Cognitive Radio (CR) Concept• Initially proposed by Mitola [2]

• Next step evolution of Software Defined Radio (SDR)

• Cognitive Radio (CR): Intelligent devices that can [2]:• Sense and autonomously reason about their environment• Adapt their communication parameters accordingly• Realize DSA concept

Cont…

In cognitive radio networks, the criterion

considered so far is in terms of protecting the primary user, i.e., maximizing the probability of detection under the constraint of probability of false alarm. In this paper, in order to formulate the sensing-throughput tradeoff problem, the objective turns out to be minimizing the probability of false alarm, under the constraint of probability of detection. We thus formulate the sensing-throughput tradeoff problem from this perspective.

IEEE 802.22 Network Architecture

IEEE 802.22 WRAN

OUTLOOK

• SYSTEM MODEL (JAWAD)• SENSING-THROUGHPUT TRADEOFF (SARMAD)• MULTI-SLOT SPECTRUM SENSING (IHSAN)• DISTRIBUTED SPECTRUM SENSING (AHMED)• COMPUTER SIMULATIONS• CONCLUSION

II. SPECTRUM SENSING PRELIMINARIES

Energy Detection

• Proposition 1:For a large N, the PDF of T(y) under hypothesisH0can be approximated by a Gaussian distribution

• Proposition 2:For a large N, the PDF of T(y) under hypothesis H1 can be approximated by a Gaussian distribution with meanμ1=(γ+1)σ2u and variance

Chi- square distribution with 2 degree of freedom

III. SENSING THROUGHPUT TRADEOFF

Sensing Throughput Tradeoff

The fundamental parameter between sensing capability and achievable throughput of the secondary networks is (TAU)

Sensing Throughput Tradeoff

• SNR of primary user =• SNR of secondary user =

• Throughputs

Sensing Throughput Tradeoff• Prob. when active =• Prob. when inactive =

Sensing Throughput Tradeoff

Sensing Throughput Tradeoff

IV. MULTI-SLOT SPECTRUM SENSING

Multi Slot Spectrum Sensing• Assumptions taken (unit mean, complex gaussian )

• Data Fusion

Multi Slot Spectrum Sensing

V. DISTRIBUTED SPECTRUM SENSING

Distributed Spectrum Sensing

VI. COMPUTER SIMULATIONS

One Secondary user for spectrum Sensing

Multi-slot Spectrum Sensing

Distributed Spectrum Sensing

VII. CONCLUSION

• Simulations shown that for a 6MHz channel, having frame duration is100ms, and the SNR ratio of primary user at the secondary receiver is−20dB,the optimal sensing time achieving the highest throughput while maintaining 90% detection probability is 14.2ms. This optimal sensing time decreases when distributed spectrum sensing is applied

REFRENCES

Sensing-Throughput Tradeoff for Cognitive Radio Networks

Ying-Chang Liang, Senior Member, IEEE, Yonghong Zeng, Senior Member, IEEE,

Edward C.Y. Peh, and Anh Tuan Hoang, Member, IEEE