## 1 Introduction  
The fifth generation mobile network [1] (5G) that is expected to be deployed in 2020 will become the main source of Internet connectivity thereafter. With the dramatic increase in the number of mobile connected devices and the endless emergence of new services, 5G research and development has also been extended [2]. 5G can increase mobile bandwidth [3] and provide a large number of machine-type communications for wireless sensors, meters, and drives. 5G should have the capacity to support a large number of connected devices and various types of traffic.  
5G requirements include extremely high data rates, very low latency, the ability to handle large numbers of devices, high reliability, energy efficiency, and reasonable cost [4]. To cope with the growing traffic demand, 5G needs to take a heterogeneous network (HetNet) architecture, as well as multiple radio access technologies [5] (RAT). Researchers have done a lot of work for this. Literature [6] designed a network selection algorithm for message transmission in security applications. Starting from the message transmission quality requirements in security application, the algorithm comprehensively considers multiple parameter indicators of message transmission service quality in security application, including end-to-end delay, packet loss rate, and transmission rate. The Communications Research Laboratory (CRL) [7] developed 60-GHz access technology in 2000, enabling the world's then-fastest data rate of 128 Mbps. Intel subsequently released the first WiGig [8] chipset. In 2014, Qualcomm released a processor combining LTE (Long Term Evolution) and WiGig standards [9]. The first wireless local area networks (WLAN) AP (Associated Press) product with WiGig standard was released in 2016 [10]. InterDigital studied a 60-GHz mesh backhaul line for junior unit base stations [11], realizing self-organizing functions through phased arrays [12]. NEC (NEC Corporation) released an E-band(71-86 GHz) transceiver that supports 10-Gbps backhaul lines to form a centralized radio frequency access network (C-RAN) [13; 14; 15]. The literature [16] proposed an optimization scheme that adopts integrated optimization ideas so that various optimization mechanisms can work cooperatively, which improves optimization efficiency by repeated utilization of network resources and information. The analog simulation results also verify the effectiveness of the optimization scheme. The related literature studies the selection and switching of ultra-dense heterogeneous networks in 5G wireless communication systems. This paper proposes a joint vertical handover method based on region-aware Bayesian decision-making, which is optimized by selecting ultra-dense heterogeneous access networks, and switching the probability to solve the problem of ultra-dense network handover. By simulating and analyzing mobile users from macro base stations entering ultra-dense service cells and different scenarios of intra-cell and inter-cell mobility, the method can accurately select the network to be switched. Thus, this solution can be applied to the application scenarios of ultra-dense networks.  
This paper presents a proof-of-concept (PoC) of millimeter-wave integrated HetNet. The study looks at millimeter-wave technology in HetNet, especially the effective utilization of 60-GHz technology. HetNet includes a traditional macrocellular network and new junior units that use millimeter waves for backhaul and link access. In addition, the concept of split control plane (CP) and user plane (UP) is introduced in HetNet [17; 18; 19; 20]. In CP/UP split HetNet, the traditional macrocell provides the CP with a large area coverage, while UP data is provided by the millimeter wave junior unit. This architecture supports uninterrupted connectivity and increases capacity by leveraging the advantages of both macro and junior cells.