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An Adaptive Subcarrier Sharing Scheme for OFDM-Based Cooperative Cognitive Radios

An Adaptive Subcarrier Sharing Scheme for
OFDM-Based Cooperative Cognitive Radios

ABSTRACT:
•                  Incorporation of orthogonal frequency division multiplexing (OFDM) in cooperative cognitive radio network facilitates subcarrier sharing to achieve spatial diversity with opportunistic spectrum access.
•      In addition, adaptive modulation has been adopted widely in wireless communication to improve spectral efficiency. Use of adaptive modulation for cooperative cognitive relaying transmission to maximize throughput under bit error rate (BER) constraint is an open issue.
•      In this paper, we propose an adaptive subcarrier sharing scheme for OFDM-based cooperative cognitive radio system, wherein cognitive (secondary) system helps the primary system to achieve its target rate of communication in exchange for opportunistic spectrum sharing.
EXISTING SYSTEM:
•           In this work, a joint optimization problem is formulated for selective subcarrier pairing and power allocation, wherein secondary system uses fraction of its subcarriers to boost the performance of primary system.
•      CSS is also based on interference limited systems , where primary system has capacity to handle additional interference from other systems without affecting its quality of service (QoS).
•       This work also determines the exact number of subcarriers that needs to be allocated by the secondary system for the primary signal transmission in order to achieve the target rate of communication for primary system in exchange for spectrum access by the secondary system.
•      Furthermore, no adaptive modulation has been used in secondary transmitter to optimize the performance of primary and secondary system.
PROPOSED SYSTEM:
•           Proposed work is the first to investigate the impact of adaptive modulation on OFDM based CSS protocol.
•      In other words instantaneous data rate with BER-SC increases, consequently outage probability decreases.
•      In other words, it not only helps the primary user to achieve the target QoS but also helps the secondary user to utilize the remaining subcarriers for its own communication.
•      The proposed scheme is applicable in dense urban scenarios where the spectrum is generally crowded and spectrum holes are hard to obtain as the performance of secondary system can be maintained regardless of availability of spectrum holes.
HARDWARE REQUIREMENTS:
•      Processor            -        Pentium –III
•      Speed                 -        1.1 Ghz
•      RAM                  -        256 MB(min)
•      Hard Disk           -        20 GB
•      Key Board          -        Standard Windows                                                          Keyboard
•      Mouse                  -        Two or Three Button                                                          Mouse
•      Monitor                -        SVGA
SOFTWARE REQUIREMENTS:
•           Tool                    -        MATLAB R2012
•      Operating system    -       Windows Xp, 7
REFERENCES:
•           J. Mitola and G. Q. Maguire, “Cognitive radio: Making software radios more personal,” IEEE Pers. Commun., vol. 6, no. 4, pp. 13–18, Aug. 1999.
•       S. Haykin and P. Setoodeh, “Cognitive radio networks: The spectrum supply chain paradigm,” IEEE Trans. Cogn. Commun. Netw., vol. 1, no. 1, pp. 3–28, Mar. 2015.
•      R. Zhang and Y.-C. Liang, “Exploiting multi-antennas for opportunistic spectrum sharing in cognitive radio networks,” IEEE J. Sel. Topics Signal Process., vol. 2, no. 1, pp. 88–102, Feb. 2008
•      V. Osa, C. Herranz, J. F. Monserrat, and X. Gelabert, “Implementing opportunistic spectrum access in LTE-advanced,” EURASIP J. Wireless Commun. Netw., vol. 2012, no. 1, pp. 1–17, 2012.








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