Multi-Carrier Listen Before Talk With Power Leakage Awareness for LTE-LAA in Unlicensed Spectrum

Licensed-assisted access (LAA) is a new feature of 3GPP LTE that utilizes unlicensed spectrum as a means of providing additional bandwidth. For fair coexistence with other incumbent systems such as Wi-Fi, LAA runs a listen-before-talk (LBT) procedure before transmission, which is designed to support multi-carrier operation as well. However, inherent power leakage to adjacent carriers ruins multi-carrier LBT and deteriorates aggregation capacity considerably. To solve this power leakage problem, we propose a hybrid design of the two LBT types of the specification to have the advantages of both, which is realized by carrier grouping, and develop an algorithm that determines division of carriers into multiple groups with a guard band in between to avoid power leakage among groups and selects the primary carrier of each group so as to maximize LAA's carrier aggregation capacity. Through extensive simulation, we demonstrate that the proposed algorithm enhances system throughput considerably over conventional mechanisms while coexisting fairly with Wi-Fi systems. We also investigate the impact of the depth of group splitting and transmit power on performance.