energy-efficient spectrum sensing and access for cognitive ...€¦ · sai wang. 2 outline ... yue...

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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●

●

●

●

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● 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 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)


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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!

energy-efficient spectrum sensing and access for cognitive ...€¦ · sai wang. 2 outline ... yue...

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