Adaptive TDD Configuration Based on Load and Channel Quality for Type-1 Inband RN in LTE-A

LTE-Advanced (LTE-A) is one of the radio access technology standards developed by the Third Generation Partnership Project (3GPP), and it is also the most popular standard of 4G/5G mobile communications technology at present. In order to extend the coverage area and provide higher transmission rates for users at the cell edge, the idea of Relay Node (RN) was proposed in LTE-A. On the other hand, two duplex modes are defined in LTE-A, namely frequency division duplex (FDD) and time division duplex (TDD), for transmission in both the uplink (UL) and downlink (DL) directions. In this paper, dynamic TDD configuration for Type-1 inband RN is addressed. Based on the input load and the channel quality, four basic schemes under the top-down and bottom-up strategies are proposed to select a proper configuration for the backhaul link and the access links. Enhanced versions of the basic schemes are also proposed, which alternate among two or three configurations in order to maximize the total capacity in the network. Simulation study demonstrates the benefit of the top-down schemes in terms of higher throughput than bottom-up schemes as well as the contrast scheme of random selection. Enhanced schemes can achieve even higher throughput than their counterpart basic schemes.