Abstract
Abstract The use of reduced power subframes in LTE Rel. 11 can improve the capacity of heterogeneous networks (HetNets) while also providing interference coordination to the picocell-edge users. However, in order to obtain maximum benefits from the reduced power subframes, setting the key system parameters, such as the amount of power reduction, carries critical importance. Using stochastic geometry, this paper lays down a theoretical foundation for the performance evaluation of HetNets with reduced power subframes and range expansion bias. The analytic expressions for average capacity and 5th percentile throughput are derived as a function of transmit powers, node densities, and interference coordination parameters in a two-tier HetNet scenario and are validated through Monte Carlo simulations. Joint optimization of range expansion bias, power reduction factor, scheduling thresholds, and duty cycle of reduced power subframes is performed to study the trade-offs between aggregate capacity of a cell and fairness among the users. To validate our analysis, we also compare the stochastic geometry-based theoretical results with the real macro base station (MBS) deployment (in the city of London) and the hexagonal grid model. Our analysis shows that with optimum parameter settings, the LTE Rel. 11 with reduced power subframes can provide substantially better performance than the LTE Rel. 10 with almost blank subframes, in terms of both aggregate capacity and fairness.
Highlights
Cellular networks are witnessing an exponentially increasing data traffic from mobile users
Given that the user equipment (UE) is located at a distance r from its macrocell of interest (MOI) and r from its picocell of interest (POI), probabilities of the UE belonging to each type can be found by integrating the conditional joint probability density function (JPDF) over the regions whose boundaries are set by the cell selection conditions in (6) to (9)
6 Conclusions In this paper, spectral efficiency and 5th percentile throughput expressions are derived for Heterogeneous network (HetNet) with reduced power subframes and range expansion
Summary
Cellular networks are witnessing an exponentially increasing data traffic from mobile users. Models based on stochastic geometry and spatial point processes provide a tractable and computationally efficient alternative for performance evaluation of HetNets [1,2,3,4]. The PPP-based models provide reasonably close performance results when compared with the real BS deployments. Results in [3] show that, when compared with real BS deployments, PPP- and hexagonal grid-based models for BS locations provide a lower bound and an upper bound, respectively, on the outage probabilities of UEs. the PPP-based models are expected to provide a better fit for analyzing denser HetNet deployments due to higher degree of randomness in small-cell deployments [2]. Due to their simplicity and reasonable accuracy, we will use PPP-based models to characterize and understand the behavior of HetNets in terms of various design parameters
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