5th International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications

Research Article

Beamforming in underlay cognitive radio: Null-shaping constraints and greedy user selection

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  • @INPROCEEDINGS{10.4108/ICST.CROWNCOM2010.9206,
        author={Eduard Jorswieck and Rami Mochaourab},
        title={Beamforming in underlay cognitive radio: Null-shaping constraints and greedy user selection},
        proceedings={5th International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications},
        publisher={IEEE},
        proceedings_a={CROWNCOM},
        year={2010},
        month={9},
        keywords={Array signal processing Cognitive radio Games Radio transmitters Receivers Signal to noise ratio},
        doi={10.4108/ICST.CROWNCOM2010.9206}
    }
    
  • Eduard Jorswieck
    Rami Mochaourab
    Year: 2010
    Beamforming in underlay cognitive radio: Null-shaping constraints and greedy user selection
    CROWNCOM
    IEEE
    DOI: 10.4108/ICST.CROWNCOM2010.9206
Eduard Jorswieck1,*, Rami Mochaourab1,*
  • 1: Communications Theory, Communications Laboratory, Dresden University of Technology, Dresden, Germany
*Contact email: Jorswieck@ifn.et.tu-dresden.de, Mochaourab@ifn.et.tu-dresden.de

Abstract

In a multiuser cognitive radio setting, multiple secondary systems coexist with multiple primary systems. We assume the secondary systems consist of transmitter-receiver pairs, and each transmitter is equipped with multiple antennas while all receivers use a single antenna. In this setting, the secondary transmitters are to operate under the constraints of producing no interference at the primary users. Such constraints on the secondary systems are referred to as null-shaping constraints. Three results are derived in this work. First, the Pareto optimal operation points for the secondary systems under null-shaping constraints are characterized by real-valued parametrization of the transmission strategies. Second, we show that all points on the Pareto boundary of the secondary systems achievable rate region without interference constraints can be achieved as the outcome of a noncooperative game by imposing certain virtual null-shaping constraints. Third, motivated by the surprising result that all Pareto efficient points can be achieved as a Nash equilibrium, we consider the problem of selecting a subset of the noncooperative secondary users for operation under the objective of maximizing their achievable sum rate. A low complexity suboptimal greedy secondary user selection algorithm is proposed and its performance is illustrated by simulations.