Cross-layer Aware TDD Frame Adaptation for FDD/TDD Carrier Aggregation in LTE-A Systems

In this paper, we study the aggregation between the FDD and TDD spectrum bands within the context of 3GPP LTE-A system. To be specific, we first provide a cross-layer design analysis to obtain the achievable throughput using the TDD mode for transmission in LTE-A system. Under particular QoS requirements and certain channel conditions, the achievable throughput is derived and evaluated. The QoS requirements originate from the upper layers, where the file size, the TCP window size and the latency for efficient transmission are incorporated in the final formulation. Having obtained the formulation, simulation results highlight the impact of the QoS parameters to different TDD frame formats. We therefore propose a framework for TDD frame adaptation within the LTE-A system. The aim of this framework is to provide the options of choosing different TDD frame formats by calculating the DL:UL subframes ratio under certain channel conditions and QoS requirements. Simulation results are carried out, which reveal the probability of choosing the different TDD frame formats from the system under certain channel conditions and QoS requirements.