Matthias Wildemeersch | Tu Twente (original) (raw)
Papers by Matthias Wildemeersch
Sustainability, 2022
Phosphorus (P) is an essential nutrient to boost crop yields, but P runoff can cause nutrient ove... more Phosphorus (P) is an essential nutrient to boost crop yields, but P runoff can cause nutrient over-enrichment in agricultural watersheds and can lead to irreversible effects on aquatic ecosystems and their biodiversity. Lake Erie is one prominent example as this watershed has experienced multiple episodes of harmful algal blooms over the last decades. Annual P loads crucially depend on yearly weather variations, which can create the risk of years with high runoff and excessive nutrient loads. Here we apply stochastic modeling to derive sustainable management strategies that balance crop yield optimization with environmental protection, while accounting for weather variability as well as weather trends as a result of climate change. We demonstrate that ignoring annual weather variations results in mitigation efforts for environmental pollution that are largely insufficient. Accounting explicitly for future variations in precipitation allows us to control the risk of emissions exceedi...
ArXiv, 2015
Vehicular networks allow vehicles to constantly share information with each other and their surro... more Vehicular networks allow vehicles to constantly share information with each other and their surrounding, and are expected to be an integral part in future intelligent transportation system (ITS). However, the diversity of ITS applications in combination with the extremely stringent demands in particular posed by safety critical applications makes the design of vehicular communication a challenging task. 5G device-to-device communication as well as 802.11p are promising to address this challenge. In order to guide and validate the design process, analytical expressions of key performance metrics such as outage probability an throughput are necessary. In this paper, we focus on the intersection scenario, and present a general procedure to analytically determine the success probability of a selected link as well as system-wide throughput. We provide an overview of the salient properties of vehicular communication systems near intersections and show how the procedure can be used to mode...
Increasing climate stress is likely to significantly impact smallholder farmer livelihoods, and c... more Increasing climate stress is likely to significantly impact smallholder farmer livelihoods, and can lead to divergent adaptation pathways. However, empirical evidence is inconclusive regarding how climate affects smallholder farmers’ deployment of various livelihood strategies, including rural-urban migration, especially as these impacts become more severe. Here we use an agent-based model to show that in a South Asian-type agricultural community experiencing a 1.5oC temperature increase by 2050, climate impacts are likely to decrease household income in 2050 by an average of 28 percent relative to the same income under a stationary climate, with fewer households engaging in economic migration and investing in cash crops. Pairing a small cash transfer with risk transfer mechanisms significantly increases the adoption of alternative livelihood strategies, improves community incomes, and reduces community inequality. While specific results depend on contextual factors such as risk pre...
In the context of social systems, diffusion processes are used to model opinion dynamics in large... more In the context of social systems, diffusion processes are used to model opinion dynamics in large-scale networks. We focus on a scenario where a set of agents has constant opinion, so-called stubborn agents, and show their impact on the final opinion formation. In the context of natural-social systems, several examples will be presented to give an overview of the range of tools used in the analysis of network resilience. For instance, the resilience of national and regional economies will be explored by analyzing the impact of extreme, low-probability and high-impact scenarios of external shocks. The behavior of the considered interconnected systems is too complex to be modeled by traditional tools, and therefore, several examples with qualitative (e.g. soft systems mapping) and quantitative (e.g. agent-based modeling) methods and approaches will be presented.
ArXiv, 2015
Diffusion processes are instrumental to describe the movement of a continuous quantity in a gener... more Diffusion processes are instrumental to describe the movement of a continuous quantity in a generic network of interacting agents. Here, we present a probabilistic framework for diffusion in networks and propose to classify agent interactions according to two protocols where the total network quantity is conserved or variable. For both protocols, our focus is on asymmetric interactions between agents involving directed graphs. Specifically, we define how the dynamics of conservative and non-conservative networks relate to the weighted in-degree Laplacian and the weighted out-degree Laplacian. Our framework allows the addition and subtraction of the considered quantity to and from a set of nodes. This enables the modeling of stubborn agents with time-invariant quantities, and the process of dynamic learning. We highlight several stability and convergence characteristics of our framework, and define the conditions under which asymptotic convergence is guaranteed when the network topol...
In the policy arena, there is high pressure to provide right and quick decisions for problems tha... more In the policy arena, there is high pressure to provide right and quick decisions for problems that are often poorly defined. There is hence an urgent need to support stakeholders in establishing a shared understanding of policy problems and to assist them in the design of potential solutions. Here we propose a formal methodology based on the construction and analysis of system maps, i.e., a graphical representation of the complex interdependencies of all relevant factors that affect the problem under study. Owing to their collaborative design, system maps provide a transparent tool with broad stakeholder acceptance to analyze ill-defined problems in a formal way. The construction of system maps involves expert elicitation to define system components, system boundaries, and interactions between system components, whereas the dynamical system behavior can be approximated by means of system dynamics. Although there is great value in the construction of the system map to enhance the und...
IEEE Transactions on Intelligent Transportation Systems
Vehicular networks allow vehicles to share information and are expected to be an integral part in... more Vehicular networks allow vehicles to share information and are expected to be an integral part in future intelligent transportation system (ITS). In order to guide and validate the design process, analytical expressions of key performance metrics such as packet reception probabilities and throughput are necessary, in particular for accident-prone scenarios such as intersections. In this paper, we analyze the impact of interference in an intersection scenario with two perpendicular roads using tools from stochastic geometry. We present a general procedure to analytically determine the packet reception probability and throughput of a selected link, taking into account the geographical clustering of vehicles close to the intersection. We consider both Aloha and CSMA MAC protocols, and show how the procedure can be used to model different propagation environments of practical relevance. We show how different path loss functions and fading distributions can be incorporated in the analysis to model propagation conditions typical to both rural and urban intersections. Our results indicate that the procedure is general and flexible to deal with a variety of scenarios. Thus, it can serve as a useful design tool for communication system engineers, complementing simulations and experiments, to obtain quick insights into the network performance.
Ecological Modelling
Recent research suggests that the spread of pest outbreaks is driven by ecological processes acti... more Recent research suggests that the spread of pest outbreaks is driven by ecological processes acting at different spatial scales. In this work, we establish a network model for the analysis and management of pest outbreaks that takes into account small-scale host-pest interactions as well as landscape topology and connectivity. The model explains outbreak cycles both for geometrid moths and bark beetles, and provides insight into the relative importance and interactions between the multi-scale drivers of outbreak dynamics. Our results demonstrate that outbreak behavior is most sensitive to changes in pest pressure at the local scale, and that accounting for the spatial connectivity of habitat patches is crucial to capturing the spreading behavior through landscapes. In contrast to early warning signals based on retrospective data, our model provides predictions of future outbreak risk based on a mechanistic understanding of the system, which we apply for landscape-scale forest management.
2016 IEEE Global Communications Conference (GLOBECOM), 2016
IFAC Journal of Systems and Control
Diffusion processes are instrumental to describe the movement of a continuous quantity in a gener... more Diffusion processes are instrumental to describe the movement of a continuous quantity in a generic network of interacting agents. Here, we present a probabilistic framework for diffusion in networks and study in particular two classes of agent interactions depending on whether the total network quantity follows a conservation law. Focusing on asymmetric interactions between agents, we define how the dynamics of conservative and non-conservative networks relate to the weighted in-degree and out-degree Laplacians. For uncontrolled networks, we define the convergence behavior of our framework, including the case of variable network topologies, as a function of the eigenvalues and eigenvectors of the weighted graph Laplacian. In addition, we study the control of the network dynamics by means of external controls and alterations in the network topology. For networks with exogenous controls, we analyze convergence and provide a method to measure the difference between conservative and non-conservative network dynamics based on the comparison of their respective attainability domains. In order to construct a network topology tailored for a desired behavior, we propose a Markov decision process (MDP) that learns specific network adjustments through a reinforcement learning algorithm. The presented network control and design schemes enable the alteration of the dynamic and stationary network behavior in conservative and non-conservative networks.
2014 Ieee Cic International Conference on Communications in China, Oct 13, 2014
Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized ... more Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous cellular network (HCN) where the macro tier and small cell tier operate according to a dynamic TDD scheme on orthogonal frequency bands. To offload the network infrastructure, mobile users in proximity can engage in D2D communications, whose activity is determined by a carrier sensing multiple access (CSMA) scheme to protect the ongoing infrastructure-based and D2D transmissions. We present an analytical framework to evaluate the network performance in terms of load-aware coverage probability and network throughput. Through the study of the tradeoff between coverage probability and D2D user activity, we provide guidelines for the optimal design of D2D network access.
Ieee Transactions on Communications, Dec 1, 2014
At present, operators address the explosive growth of mobile data demand by densification of the ... more At present, operators address the explosive growth of mobile data demand by densification of the cellular network so as to reduce the transmitter-receiver distance and to achieve higher spectral efficiency. Due to such network densification and the intense proliferation of wireless devices, modern wireless networks are interference-limited, which motivates the use of interference mitigation and coordination techniques. In this work, we develop a statistical framework to evaluate the performance of multi-tier heterogeneous networks with successive interference cancellation (SIC) capabilities, accounting for the computational complexity of the cancellation scheme and relevant network related parameters such as random location of the access points (APs) and mobile users, and the characteristics of the wireless propagation channel. We explicitly model the consecutive events of canceling interferers and we derive the success probability to cancel the n-th strongest signal and to decode the signal of interest after n cancellations. When users are connected to the AP which provides the maximum average received signal power, the analysis indicates that the performance gains of SIC diminish quickly with n and the benefits are modest for realistic values of the signal-to-interference ration (SIR). We extend the statistical model to include several association policies where distinct gains of SIC are expected: (i) maximum instantaneous SIR association, (ii) minimum load association, and (iii) range expansion. Numerical results show the effectiveness of SIC for the considered association policies. This work deepens the understanding of SIC by defining the achievable gains for different association policies in multi-tier heterogeneous networks.
2014 Ieee Global Communications Conference, Dec 8, 2014
Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL tran... more Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL transmissions has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous network (HetNet) where the macro tier and small cell tier both operate dynamic TDD and use orthogonal frequency bands. We propose a policy that leads to different associations in UL and DL, and derive the loadaware coverage probability. We evaluate how the association policy affects the system performance and derive the UL/DL configuration, base station density, and bias factor that maximize the per tier or network-wide coverage probability.
IEEE Transactions on Signal Processing, 2015
ABSTRACT In order to meet the growing mobile data demand, future wireless networks will be equipp... more ABSTRACT In order to meet the growing mobile data demand, future wireless networks will be equipped with a multitude of access points (APs). Besides the important implications for the energy consumption, the trend towards densification requires the development of decentralized and sustainable radio resource management techniques. It is critically important to understand how the distribution of signal processing operations affects the energy efficiency of wireless networks. In this paper, we provide a cross-layer framework to evaluate and compare the energy efficiency of wireless networks under different levels of distribution of the signal processing load: (i) hybrid, where the signal processing operations are shared between nodes and APs, (ii) centralized, where signal processing is entirely implemented at the APs, and (iii) fully distributed, where all operations are performed by the nodes. We find that in practical wireless networks, hybrid signal processing exhibits a significant energy efficiency gain over both centralized and fully distributed approaches.
2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2014
The densification of the network infrastructure is a possible solution to meet the explosive grow... more The densification of the network infrastructure is a possible solution to meet the explosive growth of mobile data demand. In the resulting interference-limited networks, interference management techniques are of interest to increase the spectral efficiency. Successive interference cancellation (SIC) provides modest gains when users are connected to the access point (AP) which provides the maximum average received signal power. In this paper, we focus on alternative association policies where SIC gives rise to a substantial performance gain. Specifically, we present a probabilistic framework to evaluate the performance of heterogeneous networks with SIC capabilities considering the minimum load association policy and range expansion. Numerical results show the effectiveness of SIC for these association policies.
![Research paper thumbnail of [2014 GLOBECOM]Coverage Analysis for Two-tier Dynamic TDD Heterogeneous Networks](https://attachments.academia-assets.com/49890390/thumbnails/1.jpg)
](Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL tran... more Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL transmissions has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous network (HetNet) where the macro tier and small cell tier both operate dynamic TDD and use orthogonal frequency bands. We propose a policy that leads to different associations in UL and DL, and derive the loadaware coverage probability. We evaluate how the association policy affects the system performance and derive the UL/DL configuration, base station density, and bias factor that maximize the per tier or network-wide coverage probability.
![Research paper thumbnail of [2014 ICCC]Modeling of D2D Enhanced Two-tier Dynamic TDD Heterogeneous Cellular Networks](https://attachments.academia-assets.com/49890387/thumbnails/1.jpg)
](Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized ... more Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous cellular network (HCN) where the macro tier and small cell tier operate according to a dynamic TDD scheme on orthogonal frequency bands. To offload the network infrastructure, mobile users in proximity can engage in D2D communications, whose activity is determined by a carrier sensing multiple access (CSMA) scheme to protect the ongoing infrastructure-based and D2D transmissions. We present an analytical framework to evaluate the network performance in terms of load-aware coverage probability and network throughput. Through the study of the tradeoff between coverage probability and D2D user activity, we provide guidelines for the optimal design of D2D network access.
Sustainability, 2022
Phosphorus (P) is an essential nutrient to boost crop yields, but P runoff can cause nutrient ove... more Phosphorus (P) is an essential nutrient to boost crop yields, but P runoff can cause nutrient over-enrichment in agricultural watersheds and can lead to irreversible effects on aquatic ecosystems and their biodiversity. Lake Erie is one prominent example as this watershed has experienced multiple episodes of harmful algal blooms over the last decades. Annual P loads crucially depend on yearly weather variations, which can create the risk of years with high runoff and excessive nutrient loads. Here we apply stochastic modeling to derive sustainable management strategies that balance crop yield optimization with environmental protection, while accounting for weather variability as well as weather trends as a result of climate change. We demonstrate that ignoring annual weather variations results in mitigation efforts for environmental pollution that are largely insufficient. Accounting explicitly for future variations in precipitation allows us to control the risk of emissions exceedi...
ArXiv, 2015
Vehicular networks allow vehicles to constantly share information with each other and their surro... more Vehicular networks allow vehicles to constantly share information with each other and their surrounding, and are expected to be an integral part in future intelligent transportation system (ITS). However, the diversity of ITS applications in combination with the extremely stringent demands in particular posed by safety critical applications makes the design of vehicular communication a challenging task. 5G device-to-device communication as well as 802.11p are promising to address this challenge. In order to guide and validate the design process, analytical expressions of key performance metrics such as outage probability an throughput are necessary. In this paper, we focus on the intersection scenario, and present a general procedure to analytically determine the success probability of a selected link as well as system-wide throughput. We provide an overview of the salient properties of vehicular communication systems near intersections and show how the procedure can be used to mode...
Increasing climate stress is likely to significantly impact smallholder farmer livelihoods, and c... more Increasing climate stress is likely to significantly impact smallholder farmer livelihoods, and can lead to divergent adaptation pathways. However, empirical evidence is inconclusive regarding how climate affects smallholder farmers’ deployment of various livelihood strategies, including rural-urban migration, especially as these impacts become more severe. Here we use an agent-based model to show that in a South Asian-type agricultural community experiencing a 1.5oC temperature increase by 2050, climate impacts are likely to decrease household income in 2050 by an average of 28 percent relative to the same income under a stationary climate, with fewer households engaging in economic migration and investing in cash crops. Pairing a small cash transfer with risk transfer mechanisms significantly increases the adoption of alternative livelihood strategies, improves community incomes, and reduces community inequality. While specific results depend on contextual factors such as risk pre...
In the context of social systems, diffusion processes are used to model opinion dynamics in large... more In the context of social systems, diffusion processes are used to model opinion dynamics in large-scale networks. We focus on a scenario where a set of agents has constant opinion, so-called stubborn agents, and show their impact on the final opinion formation. In the context of natural-social systems, several examples will be presented to give an overview of the range of tools used in the analysis of network resilience. For instance, the resilience of national and regional economies will be explored by analyzing the impact of extreme, low-probability and high-impact scenarios of external shocks. The behavior of the considered interconnected systems is too complex to be modeled by traditional tools, and therefore, several examples with qualitative (e.g. soft systems mapping) and quantitative (e.g. agent-based modeling) methods and approaches will be presented.
ArXiv, 2015
Diffusion processes are instrumental to describe the movement of a continuous quantity in a gener... more Diffusion processes are instrumental to describe the movement of a continuous quantity in a generic network of interacting agents. Here, we present a probabilistic framework for diffusion in networks and propose to classify agent interactions according to two protocols where the total network quantity is conserved or variable. For both protocols, our focus is on asymmetric interactions between agents involving directed graphs. Specifically, we define how the dynamics of conservative and non-conservative networks relate to the weighted in-degree Laplacian and the weighted out-degree Laplacian. Our framework allows the addition and subtraction of the considered quantity to and from a set of nodes. This enables the modeling of stubborn agents with time-invariant quantities, and the process of dynamic learning. We highlight several stability and convergence characteristics of our framework, and define the conditions under which asymptotic convergence is guaranteed when the network topol...
In the policy arena, there is high pressure to provide right and quick decisions for problems tha... more In the policy arena, there is high pressure to provide right and quick decisions for problems that are often poorly defined. There is hence an urgent need to support stakeholders in establishing a shared understanding of policy problems and to assist them in the design of potential solutions. Here we propose a formal methodology based on the construction and analysis of system maps, i.e., a graphical representation of the complex interdependencies of all relevant factors that affect the problem under study. Owing to their collaborative design, system maps provide a transparent tool with broad stakeholder acceptance to analyze ill-defined problems in a formal way. The construction of system maps involves expert elicitation to define system components, system boundaries, and interactions between system components, whereas the dynamical system behavior can be approximated by means of system dynamics. Although there is great value in the construction of the system map to enhance the und...
IEEE Transactions on Intelligent Transportation Systems
Vehicular networks allow vehicles to share information and are expected to be an integral part in... more Vehicular networks allow vehicles to share information and are expected to be an integral part in future intelligent transportation system (ITS). In order to guide and validate the design process, analytical expressions of key performance metrics such as packet reception probabilities and throughput are necessary, in particular for accident-prone scenarios such as intersections. In this paper, we analyze the impact of interference in an intersection scenario with two perpendicular roads using tools from stochastic geometry. We present a general procedure to analytically determine the packet reception probability and throughput of a selected link, taking into account the geographical clustering of vehicles close to the intersection. We consider both Aloha and CSMA MAC protocols, and show how the procedure can be used to model different propagation environments of practical relevance. We show how different path loss functions and fading distributions can be incorporated in the analysis to model propagation conditions typical to both rural and urban intersections. Our results indicate that the procedure is general and flexible to deal with a variety of scenarios. Thus, it can serve as a useful design tool for communication system engineers, complementing simulations and experiments, to obtain quick insights into the network performance.
Ecological Modelling
Recent research suggests that the spread of pest outbreaks is driven by ecological processes acti... more Recent research suggests that the spread of pest outbreaks is driven by ecological processes acting at different spatial scales. In this work, we establish a network model for the analysis and management of pest outbreaks that takes into account small-scale host-pest interactions as well as landscape topology and connectivity. The model explains outbreak cycles both for geometrid moths and bark beetles, and provides insight into the relative importance and interactions between the multi-scale drivers of outbreak dynamics. Our results demonstrate that outbreak behavior is most sensitive to changes in pest pressure at the local scale, and that accounting for the spatial connectivity of habitat patches is crucial to capturing the spreading behavior through landscapes. In contrast to early warning signals based on retrospective data, our model provides predictions of future outbreak risk based on a mechanistic understanding of the system, which we apply for landscape-scale forest management.
2016 IEEE Global Communications Conference (GLOBECOM), 2016
IFAC Journal of Systems and Control
Diffusion processes are instrumental to describe the movement of a continuous quantity in a gener... more Diffusion processes are instrumental to describe the movement of a continuous quantity in a generic network of interacting agents. Here, we present a probabilistic framework for diffusion in networks and study in particular two classes of agent interactions depending on whether the total network quantity follows a conservation law. Focusing on asymmetric interactions between agents, we define how the dynamics of conservative and non-conservative networks relate to the weighted in-degree and out-degree Laplacians. For uncontrolled networks, we define the convergence behavior of our framework, including the case of variable network topologies, as a function of the eigenvalues and eigenvectors of the weighted graph Laplacian. In addition, we study the control of the network dynamics by means of external controls and alterations in the network topology. For networks with exogenous controls, we analyze convergence and provide a method to measure the difference between conservative and non-conservative network dynamics based on the comparison of their respective attainability domains. In order to construct a network topology tailored for a desired behavior, we propose a Markov decision process (MDP) that learns specific network adjustments through a reinforcement learning algorithm. The presented network control and design schemes enable the alteration of the dynamic and stationary network behavior in conservative and non-conservative networks.
2014 Ieee Cic International Conference on Communications in China, Oct 13, 2014
Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized ... more Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous cellular network (HCN) where the macro tier and small cell tier operate according to a dynamic TDD scheme on orthogonal frequency bands. To offload the network infrastructure, mobile users in proximity can engage in D2D communications, whose activity is determined by a carrier sensing multiple access (CSMA) scheme to protect the ongoing infrastructure-based and D2D transmissions. We present an analytical framework to evaluate the network performance in terms of load-aware coverage probability and network throughput. Through the study of the tradeoff between coverage probability and D2D user activity, we provide guidelines for the optimal design of D2D network access.
Ieee Transactions on Communications, Dec 1, 2014
At present, operators address the explosive growth of mobile data demand by densification of the ... more At present, operators address the explosive growth of mobile data demand by densification of the cellular network so as to reduce the transmitter-receiver distance and to achieve higher spectral efficiency. Due to such network densification and the intense proliferation of wireless devices, modern wireless networks are interference-limited, which motivates the use of interference mitigation and coordination techniques. In this work, we develop a statistical framework to evaluate the performance of multi-tier heterogeneous networks with successive interference cancellation (SIC) capabilities, accounting for the computational complexity of the cancellation scheme and relevant network related parameters such as random location of the access points (APs) and mobile users, and the characteristics of the wireless propagation channel. We explicitly model the consecutive events of canceling interferers and we derive the success probability to cancel the n-th strongest signal and to decode the signal of interest after n cancellations. When users are connected to the AP which provides the maximum average received signal power, the analysis indicates that the performance gains of SIC diminish quickly with n and the benefits are modest for realistic values of the signal-to-interference ration (SIR). We extend the statistical model to include several association policies where distinct gains of SIC are expected: (i) maximum instantaneous SIR association, (ii) minimum load association, and (iii) range expansion. Numerical results show the effectiveness of SIC for the considered association policies. This work deepens the understanding of SIC by defining the achievable gains for different association policies in multi-tier heterogeneous networks.
2014 Ieee Global Communications Conference, Dec 8, 2014
Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL tran... more Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL transmissions has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous network (HetNet) where the macro tier and small cell tier both operate dynamic TDD and use orthogonal frequency bands. We propose a policy that leads to different associations in UL and DL, and derive the loadaware coverage probability. We evaluate how the association policy affects the system performance and derive the UL/DL configuration, base station density, and bias factor that maximize the per tier or network-wide coverage probability.
IEEE Transactions on Signal Processing, 2015
ABSTRACT In order to meet the growing mobile data demand, future wireless networks will be equipp... more ABSTRACT In order to meet the growing mobile data demand, future wireless networks will be equipped with a multitude of access points (APs). Besides the important implications for the energy consumption, the trend towards densification requires the development of decentralized and sustainable radio resource management techniques. It is critically important to understand how the distribution of signal processing operations affects the energy efficiency of wireless networks. In this paper, we provide a cross-layer framework to evaluate and compare the energy efficiency of wireless networks under different levels of distribution of the signal processing load: (i) hybrid, where the signal processing operations are shared between nodes and APs, (ii) centralized, where signal processing is entirely implemented at the APs, and (iii) fully distributed, where all operations are performed by the nodes. We find that in practical wireless networks, hybrid signal processing exhibits a significant energy efficiency gain over both centralized and fully distributed approaches.
2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2014
The densification of the network infrastructure is a possible solution to meet the explosive grow... more The densification of the network infrastructure is a possible solution to meet the explosive growth of mobile data demand. In the resulting interference-limited networks, interference management techniques are of interest to increase the spectral efficiency. Successive interference cancellation (SIC) provides modest gains when users are connected to the access point (AP) which provides the maximum average received signal power. In this paper, we focus on alternative association policies where SIC gives rise to a substantial performance gain. Specifically, we present a probabilistic framework to evaluate the performance of heterogeneous networks with SIC capabilities considering the minimum load association policy and range expansion. Numerical results show the effectiveness of SIC for these association policies.
Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL tran... more Over the last decade, mobile data traffic has risen dramatically and the amount of UL and DL transmissions has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous network (HetNet) where the macro tier and small cell tier both operate dynamic TDD and use orthogonal frequency bands. We propose a policy that leads to different associations in UL and DL, and derive the loadaware coverage probability. We evaluate how the association policy affects the system performance and derive the UL/DL configuration, base station density, and bias factor that maximize the per tier or network-wide coverage probability.
Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized ... more Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous cellular network (HCN) where the macro tier and small cell tier operate according to a dynamic TDD scheme on orthogonal frequency bands. To offload the network infrastructure, mobile users in proximity can engage in D2D communications, whose activity is determined by a carrier sensing multiple access (CSMA) scheme to protect the ongoing infrastructure-based and D2D transmissions. We present an analytical framework to evaluate the network performance in terms of load-aware coverage probability and network throughput. Through the study of the tradeoff between coverage probability and D2D user activity, we provide guidelines for the optimal design of D2D network access.