In this paper, the operation of a Licensed Shared Access (LSA) system isinvestigated, considering downlink communication. The system comprises of aMultiple-Input-Single-Output (MISO) incumbent transmitter (TX) - receiver (RX)pair, which offers a spectrum sharing opportunity to a MISO licensee TX-RXpair. Our main contribution is the design of a coordinated transmission scheme,inspired by the underlay Cognitive Radio (CR) approach, with the aim ofmaximizing the average rate of the licensee, subject to an average rateconstraint for the incumbent. In contrast to most prior works on underlay CR,the coordination of the two TXs takes place under a realistic Channel StateInformation (CSI) scenario, where each TX has sole access to the instantaneousdirect channel of its served terminal. Such a CSI knowledge setting bringsabout a formulation based on the theory of Team Decisions, whereby the TXs aimat optimizing a common objective given the same constraint set, on the basis ofindividual channel information. Consequently, a novel set of applicableprecoding schemes is proposed. Relying on statistical coordination criteria,the two TXs cooperate in the lack of any instantaneous CSI exchange. We verifyby simulations that our novel coordinated precoding scheme outperforms thestandard underlay CR approach.
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