On the Coexistence of a Primary User with an Energy Harvesting Secondary User: A Case of Cognitive Cooperation

TL;DR

This paper analyzes a cognitive radio system where an energy harvesting secondary user cooperates with a primary user, modeling queue interactions and energy dynamics to determine system stability and cooperation benefits.

Contribution

It introduces a novel model of energy harvesting secondary users cooperating with primary users, including queue interactions and stability analysis with energy constraints.

Findings

Cooperation significantly expands the system's stability region.

Energy harvesting rate impacts the secondary user's ability to assist.

Queue interactions are crucial for understanding system performance.

Abstract

In this paper, we consider a cognitive scenario where an energy harvesting secondary user (SU) shares the spectrum with a primary user (PU). The secondary source helps the primary source in delivering its undelivered packets during periods of silence of the primary source. The primary source has a queue for storing its data packets, whereas the secondary source has two data queues; a queue for storing its own packets and the other for storing the fraction of the undelivered primary packets accepted for relaying. The secondary source is assumed to be a battery-based node which harvests energy packets from the environment. In addition to its data queues, the SU has an energy queue to store the harvested energy packets. The secondary energy packets are used for primary packets decoding and data packets transmission. More specifically, if the secondary energy queue is empty, the secondary source can neither help the primary source nor transmit a packet from the data queues. The energy queue is modeled as a discrete time queue with Markov arrival and service processes. Due to the interaction of the queues, we provide inner and outer bounds on the stability region of the proposed system. We investigate the impact of the energy arrival rate on the stability region. Numerical results show the significant gain of cooperation.