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The femtocellular technology is observed to be quite promising for mobile operators as it improves their network coverage and capacity at the outskirts of the macro cell. In this paper, we have developed an analytical model for channel allocation in macro/femto-cell based BWA (Broadband Wireless Access) networks using Continuous Time Markov Chain (CTMC). The focus of the work is to analyze various QoS parameters like connection blocking probability, system capacity enhancement and channel utilization of the network for performance evaluation. We have considered a hierarchical WiMAX BWA network consisting of single macro BS along with `m' femto BS and a total number of `ch' orthogonal channels are assumed to be available in the network. The macro BS will receive the channel requests from the users either directly or via femto BS. Four types of services i.e. UGS, rtPS, nrtPS and BE request for a channel to be admitted. Pareto distribution is considered for the arrival process of the newly originated service type. The hierarchical WiMAX network is analytically modeled in the form of a `6+m' dimensional Markov Chain based on the number of admitted services of each type under macro BS and `m' femto BSs. Extensive analysis has been performed to evaluate the effectiveness and efficiency of the hierarchical WiMAX networks along with the concept of channel reuse. As per the analysis, the connection blocking probability is observed to fall drastically from about 0.8 to about 0.02 for up to 10 femto cells in the network with channel reuse. On the other hand, the system capacity and channel utilization is observed to improve acutely with the introduction of femto cells with channel reuse. Enhancement in the system capacity is observed to be up to 120% and channel utilization increases from 95% to 220% with the introduction of up to 10 femto cells in the network with channel reuse. Thus, our developed analytical model exhibits that the system performance is enhanced with th- introduction of the femto cells and the concept of channel reuse in the hierarchical WiMAX networks. The contribution of the work lies within the scope of developing an analytical model for channel allocation using CTMC to evaluate the performance of the hierarchical WiMAX networks. However, this analytical model would be equally applicable to any femto-cellular based BWA networks.