Beamforming and Rate Allocation in MISO Cognitive Radio Networks

TL;DR

This paper develops decentralized beamforming and rate allocation strategies for secondary users in MISO cognitive radio networks, optimizing secondary rates while protecting primary users under various decoding scenarios.

Contribution

It introduces a comprehensive framework for distributed optimization of secondary user performance considering different decoding methods and primary user protection constraints.

Findings

Optimal strategies depend on the decoding method used at secondary receivers.

UGD allows decoding of arbitrary user subsets, enhancing interference management.

The proposed methods improve secondary user rates while respecting primary user interference limits.

Abstract

We consider decentralized multi-antenna cognitive radio networks where secondary (cognitive) users are granted simultaneous spectrum access along with license-holding (primary) users. We treat the problem of distributed beamforming and rate allocation for the secondary users such that the minimum weighted secondary rate is maximized. Such an optimization is subject to (1) a limited weighted sum-power budget for the secondary users and (2) guaranteed protection for the primary users in the sense that the interference level imposed on each primary receiver does not exceed a specified level. Based on the decoding method deployed by the secondary receivers, we consider three scenarios for solving this problem. In the first scenario each secondary receiver decodes only its designated transmitter while suppressing the rest as Gaussian interferers (single-user decoding). In the second case each secondary receiver employs the maximum likelihood decoder (MLD) to jointly decode all secondary transmissions, and in the third one each secondary receiver uses the unconstrained group decoder (UGD). By deploying the UGD, each secondary user is allowed to decode any arbitrary subset of users (which contains its designated user) after suppressing or canceling the remaining users.