Sensing-based Resource
Allocation In Cognitive Radio
Networks
Nafiseh Jana*an Mostly based on N. Jana*an, S. Sun, and M. Modarres Hashemi, “Joint Op*mal Spectrum Sensing and Power Alloca*on in CDMA-­‐based Cogni*ve Radio Networks,” IEEE Trans. Veh. Technol., vol. 64, no. 9, pp. 3990-­‐3998, 2014. Outline
•  Cogni*ve radio concept •  Two important topics in cogni*ve radio networks •  Spectrum sensing •  Resource alloca*on •  Sensing based resource alloca*on in ✔ CDMA-­‐based cogni*ve radio networks ✘ OFDMA-­‐based cogni*ve radio networks •  Conclusion and sugges*ons 2 Motivation
3 Motivation
4 Dynamic Spectrum Access
Dynamic Exclusive Use Model Dynamic Spectrum Access Open Sharing Model Spectrum Underlay Hierarchical Access Model Spectrum Overlay Primary/Secondary User Spectrum interweave CRN Operation Models
Time Underlay Overlay Frequency 6 CR Operation Models
Time Interweave Paradigm Frequency 7 Outline
•  Cogni*ve radio concept •  Two important topics in cogni*ve radio networks •  Spectrum sensing •  Resource alloca*on •  Sensing based resource alloca*on in •  CDMA-­‐based cogni*ve radio networks •  Conclusion and sugges*ons 8 Spectrum sensing
Spectrum
Sensing
Matched filter
detection
Transmitter
detection
Receiver
detection
Energy
detection
Feature
detection
9 Spectrum sensing
•  Performance of Spectrum sensing •  Pd: Detec*on probability •  Pf: False alarm probability •  Spectrum sensing challenges 10 Cooperative spectrum sensing
•  CSS challenges •  Non ideal Sensing and Repor*ng channels •  Resource efficiency in CSS 11 Outline
•  Cogni*ve radio concept •  Two important topics in cogni*ve radio networks •  Spectrum sensing •  Resource alloca*on •  Sensing based resource alloca*on in •  CDMA-­‐based cogni*ve radio networks •  Conclusions and sugges*ons 12 Resource Allocation (RA) in CRNs
•  Wireless Resources depending on the technology •  Frequency bands •  Time slots •  Orthogonal codes •  Transmit power •  RA in interweave CRNs •  Sensing based Resource AllocaDon •  Maximize the throughput ü Minimize the energy consump*on •  Maximize the energy efficiency metric 13 Energy Consumption Minimization
•  Transmit power alloca*on in a mul*carrier-­‐CDMA network with known sensing parameters. Q. Qi, L. B. Milstein, and D. Vaman, “Cogni*ve radio based mul*-­‐user resource alloca*on in mobile adhoc networks using mul*-­‐
carrier CDMA modula*on,” IEEE J. Sel. Area Comm. , vol. 26, no. 1, pp.70–82, 2008. 14 Energy Efficiency Maximization
•  Sub-­‐channel assignment in CRN consis*ng M SUs and N sub-­‐channels, with known sensing parameters. S. Bayhan and F. Alagoz, “Scheduling in centralized cogni*ve radio networks for energy efficiency,” IEEE Trans. Veh. Technol. , vol. 62, no. 2, pp. 582 – 595, Oct. 2013. 15 Outline
•  Cogni*ve radio concept •  Two important topics in cogni*ve radio networks •  Spectrum sensing •  Resource alloca*on in cogni*ve radio networks •  Sensing based resource alloca*on in •  CDMA-­‐based cogni*ve radio networks •  Conclusion and sugges*ons 16 System Model
Sensing Repor*ng τ η Channel access T-­‐τ-­‐η 17 Spectrum sensing phase
•  Hypothesis test at the ith SUs •  is the PU’s signal which is assumed to be unknown determinis*c •  is the Gaussian noise with zero mean and variance •  is the *me index, and equals 18 Spectrum sensing phase
•  Energy detector •  On-­‐OFF Censoring Coun*ng Rule (OR) at Fusion Center 19 Transmission phase
•  Uplink CDMA (Code Division Mul*ple Access) Code 1 Code 2 Code 3 Code 4 20 Transmission phase
•  Conven*onal single user matched filter •  SIC (Successive Interference Canceller) detector at SBS 21 Problem Formulation (1)
Joint OpDmizaDon of Spectrum Sensing and Power AllocaDon Problem P1 22 Joint optimization
•  Problem P2 •  P2 is not convex in general but can be represented as a monotonic op*miza*on problem. 23 Monotonic Optimization Problem
•  Defini*on : is a Monotonic OpDmizaDon Problem iff •  are monotone increasing. •  is a close set. 24 Joint optimization
•  Problem P3 •  is an increasing and is a decreasing func*on of •  Objec*ve of P3 is a difference of increasing func*ons and can be represented as a monotonic op*miza*on problem. 25 Joint optimization
•  Problem P4 •  Polyblock/Copolyblock algorithms are suggested by Tuy for solving monotonic MaximizaDon/MinimizaDon problem. H. Tuy, “Normal sets, polyblocks and monotonic op*miza*on,” Vietnam Journal of Mathema*cs , vol. 27, no. 4, pp. 277–300, 1999. 26 Problem Formulation (2)
Separate OpDmizaDon of Spectrum Sensing and Power AllocaDon •  Problem Q1 •  Monotonic Op*miza*on Problem 27 Separate Optimization
•  Problem Q2 •  Op*mal value happens when 28 Numerical Results
•  M=5, = 0.5, = 0.95 •  Effect of sensing parameters on energy consump*on, The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer,
and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.
29 Numerical Results
•  Effect of sensing parameters on energy consump*on, 30 Numerical Results
•  Effect of fusion rule on energy consump*on 0.04 dBmJ 1.42 dBmJ 31 Numerical Results
•  Comparison of joint and separate op*miza*on 3.86 dBm 1.72 dBm 32 Numerical Results
•  Comparison of joint and separate op*miza*on 33 Outline
•  Cogni*ve radio concept •  Two important topics in cogni*ve radio networks •  Spectrum sensing •  Resource alloca*on •  Sensing based resource alloca*on in •  CDMA-­‐based cogni*ve radio networks •  Conclusion and sugges*ons 34 Conclusion
•  Spectrum sensing based resource alloca*on in CDMA-­‐based cogni*ve radio networks is considered. •  Joint and separate op*miza*on of sensing parameters and Transmiled powers are studied. •  Numerical results provided suggest that •  Joint op*miza*on method saves the energy consump*on significantly in lower sensing SNRs. •  It has a very close performance to the separate method in high sensing SNRs 35 Suggestions
•  In this work, •  uplink power alloca*on problem for the secondary users, •  A single channel cogni*ve radio network with CDMA mul*ple access of secondary users, •  Sensing *me is fixed. •  Sugges*ons, •  The downlink counterpart of the current problem, •  its extension for the the mul*-­‐channel cogni*ve radio networks, •  Op*mizing the sensing *me. 36 Thanks for your attention!
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