In this contribution, we investigate the concept of time division duplexing (TDD) mode as an alternative to underlay\r\nshort-range femtocells on the uplink of legacy macrocell deployments. To mitigate the resulting co-channel\r\ninterference, the underlaid femtocell tier uses a distributed mechanism which is based on regular busy tones and\r\nrelies on minimal signaling exchange. Stochastic geometry is used to model practical scenarios by capturing network\r\ndynamics and channel variations. The impact of the fading correlation on the performance of the coordination\r\nmechanism is examined as well. Higher-order statistics through the cumulants concept are used to recover the\r\ndistribution of the co-channel interference and evaluate the system performance in terms of the outage probability\r\nand average channel capacity. We observe that our analytical framework matches well with numerical results\r\nobtained using Monte Carlo simulations. In contrast to the uncoordinated frequency division duplexing mode, the\r\ncoordinated TDD-underlay solution shows a reduction in the outage probability of nearly 80%, while the average\r\nspectral efficiency increases by approximately 90% in high loads.
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