  Multi-stream carrier aggregation is a key technology to expand bandwidth and
improve the throughput of the fifth-generation wireless communication systems.
However, due to the diversified propagation properties of different frequency
bands, the traffic migration task is much more challenging, especially in
hybrid sub-6 GHz and millimeter wave bands scenario. Existing schemes either
neglected to consider the transmission rate difference between multi-stream
carrier, or only consider simple low mobility scenario. In this paper, we
propose a low-complexity traffic splitting algorithm based on fuzzy
proportional integral derivative control mechanism. The proposed algorithm only
relies on the local radio link control buffer information of sub-6 GHz and
mmWave bands, while frequent feedback from user equipment (UE) side is
minimized. As shown in the numerical examples, the proposed traffic splitting
mechanism can achieve more than 90% link resource utilization ratio for
different UE transmission requirements with different mobilities, which
corresponds to 10% improvement if compared with conventional baselines.
