The unprecedented growth in the number of mobile nodes, connected devices, and data traffic lead to the dense deployment of fifth generation (5G) networks. In such networks, small cells or femtocells are becoming quite popular mainly because of their features such as consistent coverage regardless of the location, transmit power adjustment, energy efficiency, and their ability of providing higher data rates compared to traditional cellular networks. Although the number of femtocells in a heterogeneous cellular network environment can be increased with an aim of satisfying high data traffic in next-generation 5G networks, higher numbers of small cell deployments may result in unnecessary, and frequent handovers. Therefore, the need for improvement and optimization of femtocell handover paradigms as well as their coexistence with other technologies should be investigated in the era of 5G cellular networks. This study proposes an analytical model which can be used to analyse integrated heterogeneous wireless cellular networks which consist femtocells. Integration of fourth and fifth generation wireless cellular systems is considered for this purpose. The state diagram of the proposed model can be represented by a two dimensional Markov Chain. A new, novel decomposition approach is employed for solving the system for state probabilities and to obtain performance measures such as mean queue length, throughput and response time. The main advantage of the new solution method is its capability of considering interaction of two systems with large queuing capacities unlike the existing matrix based solution approaches such as spectral expansion and matrix geometric methods. The proposed analytical solution approach has been validated using simulation and a system of simultaneous equations. (C) 2020 Elsevier B.V. All rights reserved.