Coordinated Shared Spectrum Precoding with Distributed CSIT

TL;DR

This paper proposes a novel coordinated precoding scheme for shared spectrum access in MISO systems, optimizing licensee rates under realistic CSI constraints and outperforming standard underlay cognitive radio methods.

Contribution

It introduces a team decision-based precoding design for spectrum sharing with distributed CSI, a novel approach in the context of LSA systems.

Findings

The proposed scheme outperforms standard underlay CR in simulations.

Coordination is achieved without instantaneous CSI exchange.

The method effectively maximizes licensee rate while respecting incumbent constraints.

Abstract

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