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Aiming at the problem of traffic surge caused by business intensive deployment in hot areas of urban environment, a three-layer cluster heterogeneous network model is constructed by densely deploying pico base stations and femto base stations on macro base stations to achieve the effect of diversion. To restrict the severe interference from inter-tier and intra-tier transmitters, an improved shared spectrum separation and allocation scheme is proposed based on cluster classification. The Poisson cluster process and the Poisson hole process are used to model the deployment of the base station, a statistical description of the interference experienced at a typical receiver is given, and then the coverage probabilities based on the validity criterion is derived. At the same time, two cascade cases such as ordered FBS association scheme and non-ordered FBS are considered. The simulation resuIts verify the correctness of the theoretical analysis and reveal the influence of network parameters on network performance. It is concluded that, compared with non-ordered FBS association scheme, ordered FBS association scheme's performance gain greatly depends on the coverage radii of PBS and FBS.. [ABSTRACT FROM AUTHOR]

In this paper, the spatial pattern of Cleistogenes squarrosa population in different restorative succession communities of the typical steppe dominated by Stipa grandis and Leymus chinensis in Inner Mongolia was measured by photography orientation, and analyzed by complete spatial randomness model, Poisson cluster process, and nested double-cluster process. In severely degraded community, C. squarrosa population fitted well nested double-cluster process for all scales, i. e. , high density small clusters existed at the centers of large clusters; whereas in 5-, 8-, and 21-year- old restored communities, C. squarrosa population fitted well Poisson cluster process for all scales, i. e. , high density small clusters did not exist at the centers of the clusters. It was suggested that facilitation was the dominant interaction in severely degraded community, while competition dominated in restored communities. The differences in the spatial pattern of C. squarrosa population during the restorative succession could be induced by the shift from facilitation to competition along the gradient of grazing stress. [ABSTRACT FROM AUTHOR]