As Prof. Khan said, the problem not about the code because it is easy to find one related to the hybrid network that you will decide to implement and you will find too many algorithms and scheme for this, but all about the idea of how to make vertical handover (parameters such as signal strength, required rate, traffic, etc, are used), techniques based on optimization, fuzzy logic, neural network usually used.
i suggest you first focus on specific hybrid network (find good papers), e.g., mmWave/Wi-Fi/LTE network, then after understanding you will find everything good