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