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A cellular hierarchical network with heterogeneous traffic is considered, where calls with shorter (longer) average call-holding time are assigned to the associated lower (upper) layer. The main contribution of this paper is that an efficient and reasonably accurate analytical method is proposed to calculate performance measures of interest, i.e., new call-blocking probability and forced termination probability for conversational services, new call-blocking probability, forced termination probability, and the average number of assigned time slots for streaming services. In particular, a simple two-state MMPP(1,2,...,K), that takes into account not only the dependence among overflowed calls of the same class but also the correlation among overflowed calls of different classes, is used to approximate overflowed traffic to reduce computational complexity and improve accuracy. The methods with the multiclass overflowed traffic being approximated as independent Poisson processes and interrupted Poisson processes are also conducted for comparison. Importantly, it is shown via simulation results that the proposed model generates more accurate results than those obtained with the other two approximation methods. Last but not least, the effect of nonuniform traffic density on performance measures is studied via simulation. It is shown that the nonuniform traffic density may have a significant impact on the performance.