Communications over Unlicensed sub-8 GHz Spectrum: Opportunities and Challenges

TL;DR

This paper reviews unlicensed sub-8 GHz spectrum, discussing regulations, technologies, applications, and interference management strategies, serving as a comprehensive resource for academia and industry.

Contribution

It provides a thorough overview of unlicensed spectrum bands below 8 GHz, highlighting regulatory considerations, technological capabilities, and interference mitigation techniques.

Findings

Shared spectrum introduces interference challenges.

Database-driven and coexistence mechanisms help manage collisions.

Unlicensed spectrum offers cost-effective connectivity solutions.

Abstract

The utilization of unlicensed spectrum presents a promising solution to the issue of spectrum scarcity in densely populated areas, while also offering a cost-effective means to connect underserved regions. In response to this potential, both academia and industry are actively exploring innovative applications of unlicensed spectrum. This work offers a thorough overview of unlicensed spectrum bands below 8 GHz, including TV White Spaces, Civil Broadband Radio Services, Industrial Scientific Medical bands, and the Unlicensed National Information Infrastructure. The paper focuses on three key aspects: regulations, existing technologies, and applications. It is essential to recognize that "unlicensed" does not equate to "unregulated"; therefore, a clear understanding of permissible and prohibited activities is crucial. From a technological perspective, we examine the current technologies, their capabilities, and relevant applications. Additionally, the shared nature of this spectrum introduces challenges related to interference among users. These collisions can be managed through two primary strategies, that we described: a database-driven approach and coexistence mechanisms at the MAC and PHY layers. This work may serve as a starting point for those who are interested in the unlicensed spectrum, both in academia and industry.