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Energy-Efficient Spectrum Sensing and Access for Cognitive Radio
Networks
Sai Wang
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Outline● Introduction● System model● Problem formulation● Simulation results● Energy-efficient techniques● Conclusion
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Why Energy Efficiency?
● Device power limitation● Transmission throughput increasing● Environment-friendly
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Energy Efficiency● Spectrum sensing● Channel switching ● Data transmission
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Constraints
● Reliability of sensing– Probability of detection
– Probability of false alarm
● Throughput– Data transmission amount are satisfied
● Delay – Data transmission speed not too slow
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Two fundamental trade-offs
● Sensing/transmission trade-off● Wait/switch trade-off
7Energy-Efficient Spectrum Sensing and Access for Cognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE, Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Problems
● The wait/switch trade-off has been largely overlooked
● Optimal spectrum access strategy is designed to maximize the throughput of the SU
● Never consider the energy constraint
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The existing scheme focus on
● Either the sensing/transmission trade-off while
neglecting spectrum hand-off● Or the wait/switch trade-off while ignoring
sensing errors.
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But...
● NO work that jointly considers spectrum sensing and hand-off for energy-efficient cognitive radio networks has been carried out!
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System model
● One primary link, one secondary link● M channels are shared with PU and SU● A frame of data:
– A sensing slot of duration
– Transmission slot
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About channel choice
● Randomly selected● However...
– Close or far from the current channel in frequency
13Energy-Efficient Spectrum Sensing and Access for Cognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE, Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Pd and Pf
Ts: the sensing timefs: sampling frequency in hertzγ : SNR Pft: target probability of false alarmPdt: target probability of detection
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Energy consumption
● Energy consumption of spectrum sensing: Ts●
●
●
●
●
● Energy consumption of total transmission: optimal Ts
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Decision making: switch or not?● Switch to another channel
– Keep transmission for T duration
● Stay on current channel– Keep transmission for T duration OR
– Waiting until the next sensing slot arrives
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Ref:Energy-Efficient Spectrum Sensing and Access forCognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE,Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Then...● Design of spectrum access strategy: minimize the
total energy cost● The energy costs depends on Ps and Ts
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The problem formulation
●The problem is formulated by finding out the optimal Ts and Ps
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Optimization problem
J: the total average energy consumption required to finish transmitting one packet of data
R: threshold for throughputD: threshold for average delay
R: the average throughputD: the average delay
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Total average energy cost
Es: the power of sensing(energy cost per second)Et: the power of data transmission(energy cost per second)P3: the probability of channel switchingJsw: energy cost for one channel switching(in the unit of joules)S: time of transmission
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The average throughput
Pc1: the probability of the channel is correctly sensed as busyP3: the probability of switching channel (1-Ps)Pe: the probability of the SU switching to a busy channelBT: the average number of bits that are transmitted in a period of Ts+TT: the transmission duration
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The average delay
Pwt: the probability that the SU waits on the current channel
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Value settings of simulation
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Simulation Results
Energy-Efficient Spectrum Sensing and Access for Cognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE, Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Energy-Efficient Spectrum Sensing and Access for Cognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE, Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Energy-Efficient Spectrum Sensing and Access for Cognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE, Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Energy-Efficient Spectrum Sensing and Access for Cognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE, Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Energy-Efficient Spectrum Sensing and Access for Cognitive Radio NetworksStephen Wang, Member, IEEE, Yue Wang, Member, IEEE, Justin P. Coon, Senior Member, IEEE, and Angela Doufexi
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Energy-efficient techniques
● Confidence voting● Cluster-Collect-Forward (CCF)
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Confidence Voting (CV)
Lee, Chia-han, and Wayne Wolf. "Energy efficient techniques for cooperative spectrum sensing in cognitive radios." Consumer Communications and Networking Conference, 2008. CCNC 2008. 5th IEEE. IEEE, 2008.
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Cluster-Collect-Forward (CCF)
Lee, Chia-han, and Wayne Wolf. "Energy efficient techniques for cooperative spectrum sensing in cognitive radios." Consumer Communications and Networking Conference, 2008. CCNC 2008. 5th IEEE. IEEE, 2008.
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Cluster-Collect-Forward (CCF)
Lee, Chia-han, and Wayne Wolf. "Energy efficient techniques for cooperative spectrum sensing in cognitive radios." Consumer Communications and Networking Conference, 2008. CCNC 2008. 5th IEEE. IEEE, 2008.
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Cluster-Collect-Forward (CCF)
Lee, Chia-han, and Wayne Wolf. "Energy efficient techniques for cooperative spectrum sensing in cognitive radios." Consumer Communications and Networking Conference, 2008. CCNC 2008. 5th IEEE. IEEE, 2008.
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Cluster-Collect-Forward (CCF)
Lee, Chia-han, and Wayne Wolf. "Energy efficient techniques for cooperative spectrum sensing in cognitive radios." Consumer Communications and Networking Conference, 2008. CCNC 2008. 5th IEEE. IEEE, 2008.
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Conclusion
● Problems● Optimal Ts and Ps → Minimum Energy
Consumption● Tradeoffs and constraints are considered● Energy-efficient techniques
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Reference
● Wang, Stephen, et al. "Energy-efficient spectrum sensing and access for cognitive radio networks." Vehicular Technology, IEEE Transactions on 61.2 (2012): 906-912.
● Lee, Chia-han, and Wayne Wolf. "Energy efficient techniques for cooperative spectrum sensing in cognitive radios." Consumer Communications and Networking Conference, 2008. CCNC 2008. 5th IEEE. IEEE, 2008.
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Thank you!
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