AWS-3 Interference Mitigation: Improving Spectrum Sharing with LTE & 5G Uplink Spectrum Control

This paper describes an interference mitigation technique known as Long Term Evolution (LTE) Uplink (UL) Frequency Avoidance (UFA). To mitigate interference LTE base stations can be configured in such a way as to force User Equipment (UE)s communicating with that base station to avoid transmitting in the passband of narrow-band victim receivers that share the same band. The UFA mechanisms include features for allocating uplink assignments within a cell sector (known colloquially as “notching”) and a second technique where the LTE block size is limited, known as Scalable Carrier Bandwidth Reduction (SCBR). The UFA techniques have been evaluated in the laboratory [1], and criteria for its use in the AWS-3 Coordination Request (CR) process have been defined. This paper describes the mechanisms to accomplish UFA within commercial grade LTE base station equipment (evolved Node B (eNodeB or eNB) and the approach to modeling the resulting emissions for interference analysis. The paper also describes how the same technique could be used in 5G networks and addresses the potential use of this technique to prevent “self-interference” by DoD tactical communications systems in constrained, congested, and contested environments where DoD deploys 4G (LTE) and 5G Radio Access Network (RAN) technologies.