A Listen before Talk Algorithm with Frequency Reuse for LTE Based Licensed Assisted Access in Unlicensed Spectrum

Abstract

This paper investigates a listen before talk (LBT) algorithm to realize both collision avoidance with nodes of other wireless systems/operators and one-cell reuse operation among nodes of the same operator for long term evolution (LTE) based licensed-assisted access (LAA) in unlicensed spectrum. When LTE system is operated in unlicensed spectrum, implementation of a LBT algorithm is required to not only follow the regulation but also realize fair coexistence with other operators' nodes or other systems' nodes, e.g. wireless local area network (WLAN), which can be operated in the same channel. However, since physical layer functionalities of LTE is designed to work in one-cell reuse operation, from the efficiency of unlicensed channels, it is preferable that LAA nodes of the same operator simultaneously transmits signals. Therefore, we study a LBT with frequency reuse which can flexibly perform collision avoidance and one-cell reuse operation according to whether the channel is idle or busy. In the proposed LBT, while applying a LBT with random backoff algorithm as the basis, each LAA node aligns the transmission timing with other LAA nodes of the same operator. Computer simulation confirms that LBT with frequency reuse can improve the throughput performances of both LAA users and WLAN users under the environment where LAA and WLAN nodes coexist.