Shadowing is believed to degrade the quality of service (QoS) in wireless cellular networks. Assuming log-normal shadowing, and studying mobile's path-loss with respect to the serving base station (BS) and the corresponding interference factor (the ratio of the sum of the path-gains form interfering BS's to the path-gain from the serving BS), which are two key ingredients of the analysis and design of the cellular networks, we discovered a more subtle reality. We observe, as commonly expected, that a strong variance of the shadowing increases the mean path-loss with respect to the serving BS, which in consequence, may compromise QoS. However, in some cases, an increase of the variance of the shadowing can significantly reduce the mean interference factor and, in consequence, improve some QoS metrics in interference limited systems, provided the handover policy selects the BS with the smallest path loss as the serving one. We exemplify this phenomenon, similar to stochastic resonance and related to the "single big jump principle" of the heavy-tailed log-nornal distribution, studying the blocking probability in regular, hexagonal networks in a semi-analytic manner, using a spatial version of the Erlang's loss formula combined with Kaufman-Roberts algorithm. More detailed probabilistic analysis explains that increasing variance of the log-normal shadowing amplifies the ratio between the strongest signal and all other signals thus reducing the interference. The above observations might shed new light, in particular on the design of indoor communication scenarios.
The impact of the shadowing on the distribution of the interference factor is studied numerically in @cite_21 and analytically in @cite_7 . However, the above two articles do not take into account the modification of the network geometry induced by the shadowing, i.e., assume that mobiles are served by their geographically closest BS. This is not a realistic assumption and, as we will show in this paper, leads to misleading conclusions that the shadowing dramatically increases the mean interference factor.
@cite_21 @cite_7
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Interference performance is among the most important issues especially in WCDMA cellular networks planning coverage and capacity. F-factor has been introduced in previous works to model the interference in WCDMA downlink dimensioning process. In this paper, we establish its PDF expression assuming 1 interferer in the server both with and without correlated shadowing effect. Uniform and non-uniform traffic situations are distinguished through the study of both uniform and non-uniform traffic load cases. Then, we generalize the expression for multiple interferers. This paper proposes an analytical study of the shadowing impact on the outage probability in cellular radio networks. We establish that the downlink other-cell interference factor, f, which is defined here as the ratio of outer cell received power to the inner cell received power, plays a fundamental role in the outage probability. From f, we are able to derive the outage probability of a mobile station (MS) initiating a new call. Taking into account the shadowing, f is expressed as a lognormal random variable. Analytical expressions of the interference factor's mean mf and standard deviation sf are provided in this paper. These expressions depend on the topology of the network characterized by a G factor. We show that shadowing increases the outage probability, and using our analytical method, we are able to quantify this impact. However, we establish that the network topology, or correlated received powers, may limit this increase.