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In typical wireless heterogeneous networks (HetNets), users are clustered around known hotspots, e.g., shopping centers or schools, but such a non-uniform distribution of nodes is difficult to analyze. This paper explicitly models this scenario, with macro base stations (MBSs) modeled by a homogeneous Poisson point process (PPP), and millimeter-wave small base stations (mmWave SBSs) and users clustered around the hotspot centers, forming two Poisson cluster processes (PCPs), respectively. Fractional frequency reuse (FFR) and coordinated multi-point transmission (CoMP) are assumed since they help to limit the co-tier interference and enhance the coverage and capacity of the network. We present a distance-based approach for grouping macro user equipments (MUEs) from the cell center (CC) and cell edge (CE) regions for FFR analysis. We first derive some distance distributions, including joint distance distribution from the typical user to the cooperative open-access mmWave SBS and distance distribution from the typical user to the non-cooperative open-access mmWave SBS. We obtain expressions for various performance metrics, including association probability, signal to interference-plus-noise ratio (SINR) coverage probability, and ergodic capacity, under these conditions. Due to the complexity of the exact expressions, we derive novel approximations, using Alzer's lemma, to obtain the lower bounds on coverage and ergodic capacity, which are shown to be accurate through Monte Carlo simulation. Simulation results analyze the effect of different parameters on the network performance to give some guidance for the design of future networks. Numerical optimization of a key parameter, in terms of association probability, coverage probability, and ergodic capacity, is enabled by our analysis. [ABSTRACT FROM AUTHOR]

In this paper, downlink non-orthogonal multiple access (NOMA) systems in large-scale cellular networks are considered and an analytical framework to evaluate the outage performance is developed. Different from the previous work where the users’ distribution is assumed to be completely independent of the Base Station (BS) locations, the deployment of the BSs and the location of NOMA-user pair are modeled as Poisson Cluster Process so that the relation between system throughput and the density of BSs could be effectively formulated and clearly revealed. Under the proposed system model, the closed-form expressions of outage probabilities are derived for 2-user downlink NOMA systems. Furthermore, the power allocation strategy is proposed for minimizing the maximal outage probability among NOMA users. And the average area spectral efficiency is also defined and derived to evaluate the throughput of the network. The accuracy of the theoretical results is verified by the simulations. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the uplink transmission performance of low-power wide-area (LPWA) networks with regards to coexisting radio modules. We adopt the long-range (LoRa) radio technique as an example of the network of focus, even though our analysis can be easily extended to other situations. We exploit a new topology to model the network, where the node locations of LoRa follow a Poisson cluster process while other coexisting radio modules follow a Poisson point process. Unlike most of the performance analysis based on stochastic geometry, we take noise into consideration. More specifically, two models, with a fixed and a random number of active LoRa nodes in each cluster, respectively, are considered. To obtain insights, both the exact and simple approximated expressions for coverage probability are derived. Based on them, area spectral efficiency and energy efficiency are obtained. From our analysis, we show how the performance of LPWA networks can be enhanced by adjusting the density of LoRa nodes around each LoRa receiver. Moreover, the simulation results unveil that the optimal number of active LoRa nodes in each cluster exists to maximize the area spectral efficiency. [ABSTRACT FROM AUTHOR]

Caching popular contents at the base stations (BSs) is a promising way to reduce the backhaul congestion. In this paper, we consider the scenario of BS cooperation for a cache-enabled HetNets where the helpers with cache are distributed around the macro BSs (MBSs). In this paper, we model the locations of the MBSs and the helpers as a Poisson point process and a Poisson hole process (PHP), respectively. Based on the proposed model, we adopt different caching and BS cooperation strategies depending on the requested file. Due to the intractability of the PHP, we adopt a fitted Poisson cluster process (PCP) to approximate the PHP, which is shown to obtain tight approximation. Based on the approximated PCP, we derive explicit expressions of the average spectrum efficiency and the area power consumption using tools from stochastic geometry. Building upon the analytical results, we then solve the problems of the area power consumption minimization and the average spectrum efficiency maximization, in which a closed-form expression for the optimal segment allocation that maximizes the average spectrum efficiency is obtained. Simulation results justify the significant gain of the proposed design compared with previously known caching schemes. [ABSTRACT FROM AUTHOR]

In heterogeneous networks, the random deployment of femto access points (FAPs) and macro base stations (MBSs) with uncoordinated channel access imposes huge intertier interferences. In real-life networks, the process of MBSs’ deployment exhibits the homogeneity; however the FAPs have the behavioral characteristic of clusters formation, such as in malls, apartments, or offices. Therefore, the composite modeling of the MBSs and the FAPs using Poisson point process and Poisson cluster process is employed for the evaluation of coverage probability. The scenario of the real-time traffic for macrotier and the best-effort traffic for femto-tier is considered. Cognition is introduced in the clustered FAPs to control the intertier interference. Furthermore, the impact of the macrotier load is analyzed by exploiting the inherent coupling between coverage probability and activity factor of an MBS. Further, we study the effect of co-channel, orthogonal, and partial spectrum sharing modes on the coverage for given parameters, such as load condition and FAPs/MBSs density. We provide simulation validation for the derived expressions of coverage and present a comparative analysis for the mentioned spectrum sharing modes. [ABSTRACT FROM AUTHOR]