License-exempt LTE systems for secondary spectrum usage: Scenarios and first assessment

Abstract

This paper investigates the feasibility and broad implications of the use of 3GPP LTE systems in license-exempt situations. License-exempt use can occur in traditional unlicensed bands or in secondary usage of white space spectrum. Various scenarios for license-exempt use are listed with a particular focus on spectrum access as a secondary user. Regulatory requirements devised by Federal Communications Commission (FCC) for TV white space usage are described and tabulated. General principles and recommendations for license exempt spectrum usage are proposed with some important scenarios being identified. Additional requirements arise out of the need to share the spectrum with other potential users in a fair manner. System simulation results in an indoor setting are used to estimate spectral efficiencies under such conditions. We conclude that LTE can be used in license-exempt secondary usage scenario with only minor modifications, such as fair sharing procedures, and could benefit from support for higher order modulations.