ws 14(1): e4

Research Article

Joint Spectrum Sensing and Resource Allocation for OFDM-based Transmission with a Cognitive Relay

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  • @ARTICLE{10.4108/ws.1.1.e4,
        author={S. Eman  Mahmoodi and K.P.  Subbalakshmi and R. Chandramouli and Bahman Abolhassani},
        title={Joint Spectrum Sensing and Resource Allocation for OFDM-based Transmission with a Cognitive Relay},
        journal={EAI Endorsed Transactions on Wireless Spectrum},
        volume={1},
        number={1},
        publisher={ICST},
        journal_a={WS},
        year={2014},
        month={4},
        keywords={cognitive radio, power allocation, spectrum sensing, subcarrier pairing, cognitive relay, OFDM},
        doi={10.4108/ws.1.1.e4}
    }
    
  • S. Eman Mahmoodi
    K.P. Subbalakshmi
    R. Chandramouli
    Bahman Abolhassani
    Year: 2014
    Joint Spectrum Sensing and Resource Allocation for OFDM-based Transmission with a Cognitive Relay
    WS
    ICST
    DOI: 10.4108/ws.1.1.e4
S. Eman Mahmoodi1, K.P. Subbalakshmi1, R. Chandramouli1, Bahman Abolhassani2
  • 1: Department of Electrical and Computer Engineering, Stevens Institute of Technology, Hoboken, NJ, USA
  • 2: Department of Electrical Engineering, Iran University of Science and Technology, Tehran, Iran

Abstract

In this paper, we investigate the joint spectrum sensing and resource allocation problem to maximize throughput capacity of an OFDM-based cognitive radio link with a cognitive relay. By applying a cognitive relay that uses decode and forward (D&F), we achieve more reliable communications, generating less interference (by needing less transmit power) and more diversity gain. In order to account for imperfections in spectrum sensing, the proposed schemes jointly modify energy detector thresholds and allocates transmit powers to all cognitive radio (CR) subcarriers, while simultaneously assigning subcarrier pairs for secondary users (SU) and the cognitive relay. This problem is cast as a constrained optimization problem with constraints on (1) interference introduced by the SU and the cognitive relay to the PUs; (2) miss-detection and false alarm probabilities and (3) subcarrier pairing for transmission on the SU transmitter and the cognitive relay and (4) minimum Quality of Service (QoS) for each CR subcarrier. We propose one optimal and two suboptimal schemes all of which are compared to other schemes in the literature. Simulation results show that the proposed schemes achieve significantly higher throughput than other schemes in the literature for different relay situations.