LTE Uplink Interference Mitigation Features

Due to the proliferation of wireless technologies over the last decade, the demand for spectrum access has grown exponentially. The Department of Defense (DoD) faces increasing pressure to free up spectrum for auction to the commercial wireless industry. The recent Advanced Wireless Services (AWS) 3 auction introduced a transition approach in which the commercial Long Term Evolution (LTE) service providers could access the spectrum incrementally with DoD coordination as DoD transitions its systems out of the band. DoD has a responsibility to maximize spectrum access to the LTE carriers while protecting mission use of existing systems in the band. As such, the DoD has been investigating creative means to coexist with commercial LTE systems during the transition. This paper describes the testing and evaluation of various innovative LTE interference mitigation techniques that can be enabled to allow DoD to coexist more readily with commercial LTE systems. The primary techniques include LTE uplink spectrum notching/blanking for traffic channels and control channels and LTE carrier aggregation (CA) configurations. The implementation methods that different equipment vendors use to achieve these techniques are distinct from one another and proprietary, adding complexity to the evaluation. This paper provides an overview of the testing and key findings of the investigation. The results include the shape of the power spectrum for different types of notching, the practical amount of spectrum that could be made available by different CA configurations, and the application of these techniques to sharing spectrum with federal government systems.