Uplink Performance of Enhanced Licensed Assisted Access (eLAA) in Unlicensed Spectrum

• Main Authors: Karaki, Reem, Jung-Fu Cheng, Obregon, Evanny, Mukherjee, Amitav, Du Ho Kang, Falahati, Sorour, Koorapaty, Havish, Drugge, Oskar
• Format: Conference Proceeding
• Language: English
• Subjects: 3GPP; Aggregates; Delays; Long Term Evolution; Sensors; Uplink; Wireless fidelity
• ISSN: 1558-2612
• DOI: 10.1109/WCNC.2017.7925553

Licensed-Assisted Access (LAA) is a new feature for 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) system to operate in the unlicensed spectrum. LAA utilizes the carrier aggregation technology to aggregate both licensed and unlicensed carriers in order to opportunistically boost user throughput, while maintaining seamless mobility, quality of service and good indoor and outdoor coverage. In order to coexist with other technologies in the unlicensed bands, several new coexistence functionalities for LAA LTE have been introduced, including long term channel selection, short-term channel sensing based on listen-before-talk (LBT), and discontinuous transmission on a carrier with limited maximum transmission duration. LAA will be supported for both Downlink (DL) and Uplink (UL) transmissions. This paper presents a detailed overview of the design challenges for UL LAA access on unlicensed bands due to the scheduling aspects of LTE. We present solutions to address grant and scheduling request (SR) overhead and delays. We also discuss possible UL LBT options to increase the performance and the flexibility of scheduled LTE when operating on unlicensed bands. A range of simulations show fair coexistence between LAA and Wi-Fi. Furthermore, this paper sheds lights on possible future enhancement for UL LAA using unscheduled UL transmission.