Co-existence of terrestrial and non-terrestrial networks (NTN) is foreseen as an important component to fulfill the global coverage promised for sixth-generation (6G) of cellular networks. Due to ever-rising spectrum demand, using dedicated frequency bands for terrestrial network (TN) and NTN may not be feasible. As a result, certain S-band frequency bands allocated by radio regulations to NTN networks overlap with those already utilized by cellular TN, leading to significant performance degradation due to the potential co-channel interference. Early simulation-based studies on different co-existence scenarios failed to offer a comprehensive and insightful understanding of the overall performance of these networks. Besides, the complexity of a brute force performance evaluation increases exponentially with the number of nodes and their possible combinations in the network. In this paper, we utilize stochastic geometry to analytically derive the performance of TN-NTN integrated networks in terms of the probability of coverage and average achievable data rate for two co-existence scenarios. From the numerical results, it can be observed that, depending on the network parameters, TN and NTN users’ distributions, and traffic load, one co-existence case may outperform the other, resulting in the optimal performance of the integrated network. The analytical results presented herein pave the way for designing state-of-the-art methods for spectrum sharing between TN and NTN and optimizing the integrated network performance.

Reconfigurable intelligent surfaces (RISs) are a promising technology for enhancing cellular network performance and yielding additional value to network operators. This paper proposes a techno-economic analysis of RIS-assisted cellular networks to guide operators in deciding between deploying additional RISs or base stations (BS). We assume a relative cost model that considers the total cost of ownership (TCO) of deploying additional nodes, either BSs or RISs. We assume a return on investment (RoI) that is proportional to the system's spectral efficiency. The latter is evaluated based on a stochastic geometry model that gives an integral formula for the ergodic rate in cellular networks equipped with RISs. The marginal RoI for any investment strategy is determined by the partial derivative of this integral expression with respect to node densities. We investigate two case studies: throughput enhancement and coverage hole mitigation. These examples demonstrate how operators could determine the optimal investment strategy in scenarios defined by the current densities of BSs and RISs, and their relative costs. Numerical results illustrate the evolution of ergodic rates based on the proposed investment strategy, demonstrating the investment decision-making process while considering technological and economic factors. This work quantitatively demonstrates that strategically investing in RISs can offer better system-level benefits than solely investing in BS densification.

Beam management is central in the operation of beamformed wireless cellular systems such as 5G New Radio (NR) networks. Focusing the energy radiated to mobile terminals (MTs) by increasing the number of beams per cell increases signal power and decreases interference, and has hence the potential to bring major improvements on area spectral efficiency (ASE). This paper proposes a first system-level stochastic geometry model encompassing major aspects of the beam management problem: frequencies, antenna configurations, and propagation; physical layer, wireless links, and coding; network geometry, interference, and resource sharing; sensing, signaling, and mobility management. This model leads to a simple analytical expression for the effective rate that the typical user gets in this context. This in turn allows one to find the number of beams per cell and per MT that maximizes the effective ASE by offering the best tradeoff between beamforming gains and beam management operational overheads and costs, for a wide variety of 5G network scenarios including millimeter wave (mmWave) and sub-6 GHz. As part of the system-level analysis, we define and analyze several underlying new and fundamental performance metrics that are of independent interest. The numerical results discuss the effects of different systemic tradeoffs and performance optimizations of mmWave and sub-6 GHz 5G deployments.

Beam management is central in the operation of dense 5G cellular networks. Focusing the energy radiated to mobile terminals (MTs) by increasing the number of beams per cell increases signal power and decreases interference, and has hence the potential to bring major improvements on area spectral efficiency (ASE). This benefit, however, comes with unavoidable overheads that increase with the number of beams and the MT speed. This paper proposes a first system-level stochastic geometry model encompassing major aspects of the beam management problem: frequencies, antennas, and propagation; physical layer, wireless links, and coding; network geometry, interference, and resource sharing; sensing, signaling, and mobility management. This model leads to a simple analytical expression for the effective ASE that the typical user gets in this context. This in turn allows one to find, for a wide variety of 5G network scenarios including millimeter wave (mmWave) and sub-6 GHz, the number of beams per cell that offers the best global trade-off between these benefits and costs. We finally provide numerical results that discuss the effects of different systemic trade-offs and performances of mmWave and sub-6 GHz 5G deployments.

As in other vertical markets, wireless communications are expected to play a fundamental role in the digitalization of the mining industry. Akin to most industrial applications, careful and scenario specific understanding of the radio propagation conditions is key to plan and deploy a reliable wireless network. However, surface mining presents an additional challenge when compared to other industrial scenarios: inherent large-scale topographic variability. Therefore, it is necessary to validate if the radio propagation models remain accurate over large topographic change. In this work, we summarize and compare the results collected in two distinct measurement campaigns, with the predictions of a dedicated path loss model (Vale Model) previously derived from measurements in surface mines. The second measurement campaign is performed by means of an automated site survey, that takes advantage of operational wireless systems and mining equipment to collect data samples. The results show that even with different transmit frequencies, topographic variation, test equipment, and measurement methods (dedicated versus automated site surveys), the Vale model provides a good fit for path loss prediction in open-pit mines, with RMSE values in the order of 7 dB. Besides, this is the first time a radio propagation model has been validated over large topographic changes in a surface mining scenario.

The mining industry is on a transition towards unmanned operations. This implies a step change in wireless infrastructure expansion to support autonomous and teleoperated machinery. This paper investigates how the topographic changes over the course of 10 years of continuous mining affect the propagation conditions, and impacts the performance associated with different deployment strategies for wireless networks in a large open-pit mining complex in Brazil. Through a series of system-level simulations, using detailed terrain models, realistic traffic volumes and a dedicated propagation model, we compare the ability of different deployment strategies, and network features, to meet given performance targets with existing technology. The results show that heterogeneous deployments can be exploited to continuously guarantee coverage in this ever- changing topography, while interference mitigation techniques, such as enhanced inter-cell interference coordination (eICIC) and beamforming, can be used to reduce the system outage without need to increase the spectrum.

This paper analyzes the effects of shadowing in vehicle-to-infrastructure (V2I) links caused by haul trucks in surface mines. The work focuses on mobile cell sites, known as cell on wheels (COWs), which are widely used by the mining industry. The study relies on extensive ray tracing simulations based on realistic 3D CAD models and detailed propagation effects. The results are presented in terms of excess path loss for multiple frequency bands, namely 795 MHz, 2.6 GHz, 5.9 GHz and 28 GHz. As expected, blockage is very severe for mmW transmissions, but our results show that even sub-1 GHz links may suffer shadowing losses exceeding 20 dB under unfavorable conditions, e.g. haul trucks lifting the dump bed. The results can also guide future measurement campaigns and provide useful insights for engineers planning and optimizing mission-critical wireless networks in mines.

In this paper, we investigate the suitability of the propagation models ITU-R 526, Okumura Hata, COST Hata models and Standard Propagation Model (SPM) to predict the path loss in open-pit mines. The models are evaluated by comparing the predicted data with measurements obtained in two operational iron-ore mining complexes in Brazil. Additionally, a simple deterministic model, based on the inclusion of an effective antenna height term to the ITU-R 526, is proposed and compared to the other methods. The results show that the proposed model results in root-mean-square error (RMSE) values between 5.5 dB and 9.2 dB, and it is capable of providing a close approximation of the best predictions (i.e. those with lowest RMSE) as provided by the SPM. The proposed model, however, reduces the calibration complexity considerably.

In this paper we present the results of an extensive measurement campaign performed at two large iron ore mining centers in Brazil at the 2.6 GHz band. Although several studies focusing on radio propagation in underground mines have been published, measurement data and careful analyses for open-pit mines are still scarce. Our results aim at filling this gap in the literature. The research is motivated by the ongoing mine automation initiatives, where connectivity becomes critical. This paper presents the first set of results comprising measurements under a gamut of propagation conditions. A second paper detailing sub-GHz propagation is also in preparation. The results indicate that conventional wisdom is wrong, in other words, radio-frequency (RF) propagation in surface mines can be far more elaborate than plain free-space line-of-sight conditions. Additionally, the old mining adage “no two mines alike” seems to remain true in the RF domain.

This work presents an investigation on the use of the IEEE 1902.1 (RuBee) protocol in order to communicate with buried assets. This is an important requirement in some applications, particularly in the mining industry. RuBee is a low-rate protocol, but its ability to transmit through solid material makes it the first choice for this kind of application. By means of an event-driven simulation, we evaluate the performance of RuBee in different scenarios, in which several buried tags attempt to communicate with a surface reader.

The ideal successive interference cancellation paradigm helps to achieve the capacity of some multiuser channels, such as the Gaussian multiple access and broadcast channels. However, its performance is much more modest under realistic constraint on the decodability of the interference signal. In this paper, we rely on basic stochastic geometry models to analytically evaluate the performance of interference cancellation receivers in a local area network scenario, under `realistic' rate-constraints on the decodability of the interference signal. Analytical findings are validated by extensive Monte Carlo experiments. Alongside, complementary system level simulations results are presented to demonstrate the performance in a `practical'-like system. Our findings explicitly quantify how the gains from interference cancellation techniques depend on the spatial density of the active interferers in the network, and their respective data rates. The findings further highlight the importance of properly dimensioning the system in order to fully benefit from such interference cancellation techniques.

WiFi is the prevalent wireless access technology in local area deployments and is expected to play a major role in a mobile operator's data offloading strategy. As a result, having simple tools that are able to assess the offloading potential of IEEE 802.11 networks is vital. In this paper, we propose a simple closed-form solution to calculate down- and uplink throughput values per user under full-buffer traffic when small WiFi cells are used to offload macrocells. Extensive measurement campaigns and simulation results demonstrate that there is an excellent quantitative match between analytical model and data despite the simplicity of the former. Finally, in light of our observations we discuss some of the fundamental technological limitations that may have a significant impact on the future of small cells.

This paper addresses carrier-based inter-cell interference coordination (CB-ICIC) among LTE femtocells operating on a single carrier. CB-ICIC is in many ways linked to the widely investigated dynamic channel assignment problem, which is often studied in the context of graph coloring. The investigation revolves around the sensible definition of the underlying graph, i.e. the network model, rather than focusing on the coloring algorithms and their properties. Ultimately, we posit that improper online graph-coloring suffices and is actually preferable. In short, settling for less-than-optimal configurations avoids uncontrolled service interruptions. Such disruptions tend to raise understandable concerns when it comes to fully autonomous selection of operational CCs. Our results dispel such concerns by showing that conservative methods can achieve most of the benefits of unrestricted off-line coloring algorithms with a very modest number (2-3) of CCs to choose from.

This paper addresses the interference management problem in the context of LTE-Advanced femtocells. Due to the expected large number of user-deployed cells, centralized network planning becomes increasingly less viable. Consequently, we consider an architecture of autonomous decision makers. Our main contribution in this paper, denominated Generalized Autonomous Component Carrier Selection (G-ACCS), is a distributed carrier-based inter-cell interference coordination scheme that represents one step towards cognitive radio networks. The algorithm relies on expected rather than sensed interference levels. This approach facilitates scheduler-independent decisions, however, it can lead to overestimation of the interference coupling among cells when the resources are not fully utilized. Acknowledging this fact, G-ACCS leverages the power domain to circumvent the restrictive nature of expected interference coupling. This work focuses on the downlink and also provides an extensive characterization of the network performance as a function of the topology as well as the often overlooked temporal traits of traffic. We compare G-ACCS with other carrier-based solutions, including the simplest universal reuse strategy. The encouraging simulation results demonstrate that G-ACCS achieves an efficient and fair distribution of resources in all considered traffic and deployment conditions. More importantly, this is attained in a truly autonomous fashion, without any explicit parametrization.

Dynamic spectrum approaches are steadily gaining momentum, especially in the context of femtocells. Yet designing efficient, stable, fair and scalable distributed algorithms is no easy feat, specially if the cells in a wireless network tend to act selfish and independently. Game Theory is a powerful toolbox which models the interaction of autonomous agents. In this paper we present a game theoretic model for a dynamic spectrum sharing framework recently proposed for femtocells. Our analysis includes cases where femtocells compete for spectrum as well as cooperative cases towards a common goal. The system level simulation results show that strict adherence to the game-theoretic selfish behavior performs poorly compared to the non-adherent rules which balance altruism and rational egoism. The main conclusion is that practical solutions should be guided but not limited by purely theoretical assumptions.

In this paper we investigate uplink carrier aggregation in the context of dense residential deployments of LTE-Advanced Femtocells. Previous work in the literature based on macro-cells suggested considering UE power limitations to infer which UEs should be allowed to employ multiple component carriers. However, due to the very small radius of femtocells, UEs are not expected to become power-limited at all. We propose a decentralized scheme with limited signalling requirements that incorporates power control information, not only to guide the UE-specific carrier selection procedure, but also to capitalize on the inherent power spectral density and path loss differences in order to minimize inter-cell interference. We present a series of system level simulation results which provide strong evidence that our scheme delivers substantial gains in terms of coverage compared to existing solutions without sacrificing the SINR.

The increasing popularity of the femtocell concept has revamped the interest in dynamic interference coordination techniques for dense and uncoordinated deployments of low- power home base stations. One of the proposed schemes for 4G OFDMA femtocells is known as Autonomous Component Carrier Selection (ACCS). ACCS capitalizes on the carrier aggregation framework of LTE-Advanced to curb inter-cell interference levels. Albeit being exclusively based on downlink information, previous contributions attested the effectiveness of the scheme in the uplink as well. This paper extends the initial argumentation by including uplink information into the component carrier selection process. We assess and discuss the uplink performance of two proposed variants of ACCS via extensive system level simulations. The striking conclusion based on the results is that the mere addition of uplink information, which is difficult to estimate in the real world, does not provide substantial performance improvements.

The recent introduction of carrier aggregation in LTE-Advanced enables new possibilities in designing frequency domain interference reduction and management schemes. These methodologies are of extreme interest in the case of dense and uncoordinated deployments of femtocells. In such scenarios, dense deployment of cells coupled with the scarcity of frequency resources may lead to a potentially disruptive amount of interference, which severely affects the performance of the system. This contribution presents a novel method inspired by graph and coalitional game theories. The proposed algorithm consists of a set of distributed and scalable rules for building coalitions; these rules essentially resolve the conflicts among avid femtocells competing for a limited amount of resources. The proposed scheme has been designed by targeting localized reconfigurations, thus avoiding reconfiguration storms in the network. Furthermore, the rules governing the resource redistribution ensure overall system performance improvements while maintaining a certain degree of fairness among the competing nodes. Simulation results prove the effectiveness of the proposed method.

It has been identified in numerous contributions that dynamic interference coordination is very appealing in case of dense and uncoordinated deployments of home eNBs, also known as femtocells. One of the proposed schemes for LTE-Advanced is known as Autonomous Component Carrier Selection (ACCS). Previous contributions presented extensive downlink performance results attesting the effectiveness of ACCS. Nonetheless, the uplink has its own set of specificities, such as the use of Fractional Power Control (FPC). In this light, the purpose of this paper is two-fold: (i) Provide qualitative and quantitative answers to questions such as what is the impact of FPC on femtocells and how to best configure it. (ii) Evaluate in detail the uplink performance of ACCS under realistic power control settings. Using results derived from extensive uplink system level simulations we show that the behavior of FPC when applied to femtocells is significantly different from that seen on macrocells. In addition we demonstrate that ACCS is equally attractive and applicable to the uplink even though most decisions are based on UE downlink measurements.

Low-power home base stations, also known as femtocells, are one of the strong candidates for high data rate provisioning in indoor environments. Unfortunately, the benefits are not without new challenges in terms of interference management and efficient system operation. In this paper we take a closer look at several aspects associated with the deployment of LTE-Advanced home eNBs under two different access policies: closed subscriber group (CSG) and open subscriber group (OSG). Our results are derived from extensive downlink system level simulations. We limit our scope to dense-urban deployment of femtocells assuming dedicated carriers, i.e. no interference to/from the macro layer. Particularities of each access mode are discussed under different hard frequency re-use configurations. Our results indicate that an OSG deployment is indeed able to cut short the lower end of the SINR distribution when universal frequency re-use is employed. However, when other re-use configurations are considered, OSG no longer guarantees improved SINR conditions. In addition, we present additional results for the autonomous component carrier selection (ACCS) concept introduced in earlier contributions, providing strong suggestions that the scheme yields attractive performance benefits independently of the access policy selected by the operator. Finally, we point out that uplink results including realistic power control settings need to be considered before definitive conclusions can be safely drawn.

Uncoordinated deployment of eNBs in local area environments will benefit from having support for dynamic frequency re-use mechanisms also known as "autonomous component carrier selection", where each eNB dynamically selects to use only a subset of the available component carriers (i.e. using from one component carrier up to the maximum number of available component carriers). Component carriers are selected autonomously by each eNB depending on the offered traffic, interference coupling with neighboring cells, etc. In this contribution we propose a simple and distributed scheme based on so-called background interference matrices (BIMs) for autonomous component carrier selection. Extensive numerical simulation campaigns indicate that the proposed scheme effectively allows each eNB to select the most attractive frequency configuration; improving average user capacity and boosting cell edge performance considerably.

LTE-advanced systems, which aim to provide high data rate wireless services, have received world-wide researching interests nowadays. In this paper, the performance of fixed frequency reuse with different reuse factors is studied in LTE-advanced systems. Performance is measured in terms of both average cell throughput and cell edge user throughput. It is found that a properly chosen reuse factor with respect to cell size (which leads to different level of inter-cell interference), can offer up to 30% gain in average cell throughput and much higher gain for cell-edge user throughput in local area (LA). This high gain from frequency reuse makes it attractive for future LTE-advanced systems.

In order to accommodate the growing traffic demand in GSM cellular networks, several features are continuously being developed to improve the voice capacity of GSM/EDGE radio access network (GERAN). In this paper we investigate the capacity of a GSM network considering the use of some of these features, namely, interference rejection combining (IRC), single-antenna interference cancellation (SAIC), source-adaptive AMR (SA-AMR), dynamic frequency and channel allocation (DFCA), and 8-PSK voice channels. These techniques have been previously investigated individually in the literature, but here we focus on the system-level impact of the interactions among them. We show that the proper combination of these features increases the spectral efficiency of speech channels in GERAN.

This study devises a simple mathematical model that predicts the number of beams that maximizes system capacity for different WCDMA network configurations. The ideal number of beams to be synthesized within a cell by an antenna array (AA) with a fixed number of elements at the base station (BS) is primarily influenced by the average antenna gain and the relative power allocated to the secondary common pilot channel (S-CPICH) transmitted on each directional beam. It is shown that for a fixed maximum Node-B transmit power the overall system capacity gain in the downlink (DL) provided by switched beam forming (SBF) decreases with the cell size, that is, as more power is needed by the pilot channels to assure coverage. Predictions from our model are compared with simulation results obtained from a detailed dynamic system level simulator in order to be validated. A remarkably good match is observed

We analyse the downlink (DL) cell throughput for a WCDMA system using switched beamforming (SBF) with 4-element antenna array at the base station (node-B) and dual antenna (2Rx) user equipment (UE). We investigate the performance as a function of the penetration rate of 2Rx UEs. The performance assessment is conducted with dynamic system simulations, which are supplemented with simple theoretical analysis. Code blocking (CB) occurs when a UE is denied access in the cell due to lack of a DL channelisation code under the primary scrambling code for that cell. When the code-blocking problem is circumvented, it is observed from the simulation results that at 100% penetration rate of 2Rx UEs, the combined feature offers more than the multiplicative gain in the capacity improvement. The numerical result obtained from the theoretical analysis complements the simulation results. The SBF-2Rx code-unrestricted (CU) capacity gain is 327% compared to a 3-sector single directional antenna transmission at the node-B and single antenna reception at the UE