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Network slicing is a central feature in 5G and beyond systems to allow operators to customize their networks for different applications and customers. With network slicing, different logical networks, i.e. network slices, with specific functional and performance requirements can be created over the same physical network. A key challenge associated with the exploitation of the network slicing feature is how to efficiently allocate underlying network resources, especially radio resources, to cope with the spatio-temporal traffic variability while ensuring that network slices can be provisioned and assured within the boundaries of Service Level Agreements / Service Level Specifications (SLAs/SLSs) with customers. In this field, the use of artificial intelligence, and, specifically, Machine Learning (ML) techniques, has arisen as a promising approach to cater for the complexity of resource allocation optimization among network slices. This paper tackles the description of a feasible implementation framework for deploying ML-assisted solutions for cross-slice radio resource optimization that builds upon the work conducted by 3GPP and O-RAN Alliance. On this basis, the paper also describes and evaluates an ML-assisted solution that uses a Multi-Agent Reinforcement Learning (MARL) approach based on the Deep Q-Network (DQN) technique and fits within the presented implementation framework., This work has been supported by the Spanish Research Council and FEDER funds under SONAR 5G grant (ref. TEC2017-82651-R) and by the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia under grant 2019FI_B1 00102., Peer Reviewed, Postprint (published version)

Network slicing is a fundamental feature of 5G systems that allows the partitioning of a single network into a number of segregated logical networks, each optimized for a particular type of service, or dedicated to a particular customer or application. While support for network slicing (e.g. identifiers, functions, signalling) is already defined in the latest 3GPP Release 15 specifications, solutions for efficient automated management of network slicing (e.g. automatic provisioning of slices) are still at a much more incipient stage, especially for what concerns the next-generation Radio Access Network (NG-RAN). In this context, and consistently with the new service-based management architecture defined by 3GPP for 5G systems, this paper presents a functional framework for the management of network slicing in a NG-RAN infrastructure, delineating the interfaces and information models necessary to support the dynamic and automatic deployment of RAN slices. A discussion on the complexity of such automation follows together with an illustrative description of the applicability of the overall framework and information models in the context of a neutral host provider scenario that offers RAN slices to third party service providers., Peer Reviewed, Postprint (published version)

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., This work has been supported by the Spanish Research Council and FEDER funds under SONAR 5G grant (ref. TEC2017-82651-R)., Peer Reviewed, Postprint (author's final draft)

Network slicing is a key capability of 5G networks that facilitates the provision of multi-tenancy by allocating different slices to the tenants that share a certain infrastructure according to specific Service Level Agreements (SLAs). In this context, this paper focuses on radio admission control as the function that controls the amount of radio resources assigned to the different tenants in a 5G radio access network. Specifically, a novel approach is proposed that includes profit-related metrics in the decision-making process, accounting for the additional extra incomes that can be obtained by sporadically granting additional capacity beyond the SLA level and for the penalties incurred due to potential SLA breaches. The proposed approach is evaluated by means of simulations to assess its benefits in terms of achieved profit and throughput., Peer Reviewed, Postprint (published version)

This paper discusses the exploitation of data analytics for supporting the operation of Radio Resource Management (RRM) in the Next Generation Radio Access Network (NG-RAN), analysing the need for standardised and open frameworks and the specific characteristics of the NG-RAN that impact on the design of data analytics solutions. As a practical example of this concept, a simple but illustrative use case is presented, which intends to enhance the Radio Admission Control (RAC) function with data analytics information in scenarios with both Fixed Wireless Access (FWA) users and mobile users. A functional framework for the realization of the proposed solution is described and the performance of the RAC algorithm is evaluated under different scenario conditions to better delimitate its potential., Peer Reviewed, Postprint (published version)

Network slicing is a fundamental feature of 5G systems that facilitates the provision of particular system behaviours adapted to specific service/application domains on top of a common network infrastructure. A network slice is in general composed by a core network slice and a Radio Access Network (RAN) slice. The realization of RAN slices is particularly challenging because it requires configuring and operating traffic differentiation and protection mechanisms to simultaneously deliver multiple and diverse RAN behaviors over a given pool of radio resources. In this context, this paper proposes to characterize the behavior of a RAN slice through the specification of a set of control parameters that are used to dictate the operation of the packet scheduling function at Layer 2 and the radio admission control function at Layer 3. An evaluation of the suitability of these parameters for achieving efficient radio resource sharing and isolation between RAN slices is presented when configuring a network for supporting a slice with multiple enhanced Mobile BroadBand services and another slice for providing Mission Critical services. The analysis reveals the different impact of the Layer 3 and Layer 2 parameters for isolating services of different slices depending on whether they require guaranteed or non-guaranteed bit rates., Peer Reviewed, Postprint (published version)

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., Multi-tenant Radio Access Networks (RANs) are envisaged to play a key role in highly dense scenarios for fulfilling the challenging capacity requirements of future enhanced Mobile BroadBand services while reducing the capital and operational costs per tenant. In this context, this paper proposes a self-optimized Admission Control (AC) strategy for automatically adjusting the share of resources per tenant in each cell of the shared RAN in order to account for uneven time/space distributions of tenants’ traffic demand across cells. The proposed approach is evaluated by means of simulations to analyze the operation of the self-optimization process under different traffic distributions. Results reveal that the proposed self-optimized AC can provide substantial throughput gains of up to 65% with respect to the case without self-optimization., Peer Reviewed, Postprint (author's final draft)

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., Network slicing is a fundamental feature of 5G systems that facilitates the provision of particular system behaviours adapted to specific service/application domains on top of a common network infrastructure. While significant progress has already been achieved at specification level by 3GPP with regard to the functional support of network slicing, management solutions for the exploitation of these capabilities in the NG-RAN are still at a very incipient stage. In this context, this paper firstly presents a functional framework for the management of network slicing for a NG-RAN infrastructure, identifying the necessary information models and interfaces to support the dynamic provisioning of RAN slices. On this basis, the feasibility to automate the provisioning of RAN slices is discussed. Furthermore, a self-planning solution is presented to illustrate how a traditional network management process such as planning is expected to evolve to cope with the new challenges associated with RAN slicing management., Peer Reviewed, Postprint (author's final draft)

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., Network slicing is a fundamental capability for future Fifth Generation (5G) networks to facilitate the cost-effective deployment and operation of multiple logical networks over a common physical network infrastructure in a way that each logical network (i.e. network slice) can be customized and dimensioned to best serve the needs of specific applications (e.g. mobile broadband, smart city, connected car, public safety, fixed wireless access) and users (e.g. general public, enterprise customers, virtual operators, content providers). The practical realization of such capability still raises numerous technical challenges, both in the Core and RAN parts of the 5G system. Through a comprehensive analysis of the impact that the realization of RAN slicing has on the different layers of the radio interface protocol architecture, this article proposes a framework for the support and specification of RAN slices based on the definition of a set of configuration descriptors that characterize the features, policies and resources to be put in place across the radio protocol layers of a next-generation RAN node., Peer Reviewed, Postprint (author's final draft)

©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., This paper aims to improve the user Quality of Service (QoS) in 5G networks by introducing a user-centric view that exploits the predictability of the user’s daily motifs. An agglomerative clustering is used to identify these motifs according to the cells in which the user is camping during the day. Then, a technique to extract the personalised QoS observed by the user is proposed. The methodology is illustrated with an example that makes use of real measurements obtained from a specific customer of a 3G/4G operator. The presented results illustrate that the proposed user-centric approach is able to identify situations with poor user perceived QoS which could not be identified by a classical network-centric approach., Peer Reviewed, Postprint (author's final draft)

The sharing of Radio Access Networks is gaining momentum in small cell scenarios, due to the associated reduction in capital and operational costs. In this scenario, the split of radio resources among tenants sharing the network becomes a fundamental problem to provide each one with its required capacity. In this respect, this paper proposes a multi-tenant admission control scheme for performing this split with the target of ensuring an efficient use of the radio resources by exploiting traffic multiplexing principles at both intra-cell and multi-cell level in order to cope with heterogeneities in the spatial traffic distribution of the different tenants. A simulation-based analysis is presented to assess the flexibility of the proposed approach under different traffic mixes of the different tenants in each cell. Substantial bit rate improvements (e.g. up to 106%) and blocking probability reductions are obtained with respect to a baseline scheme., Peer Reviewed, Postprint (published version)

This paper addresses the implementation of Radio Resource Management (RRM) and Self-Organizing Networks (SON) functions in virtualized multi-tenant small cell networks. In this context, the deployment and operation of RRM/SON functions as virtualized services facilitates the customization of the Radio Access Network (RAN) on a per-tenant basis. Specifically, this paper develops the architectural and functional framework for virtualizing RRM/SON functions, together with the illustration of some examples assessing the orders of magnitude of the requirements of the involved Virtual Network Functions (VNF), Peer Reviewed, Postprint (published version)

Network slicing is a fundamental capability for future 5G networks to properly support current and envisioned future application scenarios. Network slicing facilitates a cost-effective deployment and operation of multiple logical networks over a common physical network infrastructure such that each network is customized to best serve the needs of specific applications (e.g., mobile broadband, Internet of Things applications) and/or communications service providers (e.g., special purpose service providers for different sectors such as public safety, utilities, smart city, and automobiles). Slicing a RAN becomes particularly challenging due to the inherently shared nature of the radio channel and the potential influence that any transmitter may have on any receiver. In this respect, this article analyzes the RAN slicing problem in a multi-cell network in relation to the RRM functionalities that can be used as a support for splitting the radio resources among the RAN slices. Four different RAN slicing approaches are presented and compared from different perspectives, such as the granularity in the assignment of radio resources and the degrees of isolation and customization., Peer Reviewed, Postprint (author's final draft)

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., The introduction of multi-tenancy in the Radio Access Network (RAN) is seen as a relevant capability of future 5G systems to support the challenging capacity requirements in a cost-effective way. Multi-tenancy brings in new challenges in the way how the RAN has to be managed and operated in order to provide the agreed service levels to each tenant and at the same time achieve an efficient utilization of the radio resources. This paper proposes a new solution for flexible capacity sharing among tenants based on a hybrid centralized/distributed Self- Organizing Network (SON) function to automatically adjust the Admission Control (AC) settings of the different cells. The proposed solution makes use of fuzzy neural controllers that provide intrinsic benefits in terms of dealing with the uncertainties of complex cellular scenarios and introducing the formulation of preferences and policies in the decision process. Together with the detailed description of the different components of the proposed solution, the paper presents an initial evaluation that provides sufficient insight into the potentials of the fuzzy neural hybrid SON to stimulate further and subsequent analysis., Peer Reviewed, Postprint (author's final draft)

This paper considers the use of clustering techniques to learn the mobility patterns existing in a cellular network. These patterns are materialized in a database of prototype trajectories obtained after having observed multiple trajectories of mobile users. Both K-means and Self-Organizing Maps (SOM) techniques are assessed. Different applicability areas in the context of Self-Organizing Networks (SON) for 5G are discussed and, in particular, a methodology is proposed for predicting the trajectory of a mobile user., Peer Reviewed, Postprint (published version)

Self-Organizing Network (SON) functionalities in forthcoming 5G systems stand as a promising field for the fertilization of Artificial Intelligence (AI) mechanisms. In this respect, this paper analyzes how SON functionalities for radio access network planning and optimization in future 5G systems can be built upon AI concepts. A framework is presented that processes input data from multiple sources and extracts, through learning-based classification, prediction and clustering models, relevant knowledge to drive the decisions made by 5G SON functionalities. Different candidate AI-based tools for knowledge discovery are identified together with the associated knowledge models that can be extracted. On this basis, the applicability of these models to a comprehensive range of 5G SON functions across the categories of self-planning, self-optimization and self-healing is analyzed. Finally, the paper identifies the research directions deriving from the proposed framework., Peer Reviewed, Postprint (published version)

This paper presents a vision of how the different management procedures of future Fifth Generation (5G) wireless networks can be built upon the pillar of artificial intelligence concepts. After a general description of a cellular network and its management functionalities, highlighting the trends towards automatization, the paper focuses on the particular case of extracting knowledge about the time domain traffic pattern of the cells deployed by an operator. A general methodology for supervised classification of this traffic pattern is presented and it is particularized in two applicability use cases. The first use case addresses the reduction of energy consumption in the cellular network by automatically identifying cells that are candidates to be switched-off when they serve low traffic. The second use case focuses on the spectrum planning and identifies the cells whose capacity can be boosted through additional unlicensed spectrum. In both cases the outcomes of different classification tools are assessed. This capability to automatically classify cells according to some expert guidance is fundamental in future networks, where an operator deploys tenths of thousands of cells, so manual intervention of the expert is unfeasible., Peer Reviewed, Postprint (published version)

This paper focuses on a heterogeneous scenario in which cellular and wireless local area technologies coexist and in which mobile devices are enabled with device-to-device communication capabilities. In this context, this paper assumes a network architecture in which a given user equipment (UE) can receive mobile service either by connecting directly to a cellular base station or by connecting through another UE that acts as an access point and relays the traffic from a cellular base station. The paper investigates the optimization of the connectivity of different UEs with the target to minimize the total transmission power. An optimization framework is presented, and a distributed strategy based on Q-learning and softmax decision making is proposed as a means to solve the considered problem with reduced complexity. The proposed strategy is evaluated under different conditions, and it is shown that the strategy achieves a performance very close to the optimum. Moreover, significant transmission power reductions of approximately 40% are obtained with respect to the classical approach, in which all UEs are connected to the cellular infrastructure. For multi-cell scenarios, in which the optimum solution cannot be easily known a priori, the proposed approach is compared against a centralized genetic algorithm. The proposed approach achieves similar performance in terms of total transmitted power, while exhibiting much lower computational requirements., Peer Reviewed, Postprint (author's final draft)

Small Cell as a Service (SCaaS) is envisaged as a solution to facilitate the provisioning of shared radio access capacity to mobile operators in areas where dedicated per-operator deployments may be impractical, typically highly densified scenarios such as stadiums, malls, office buildings, etc. In this context, this paper firstly establishes a reference framework for SCaaS provisioning from the Radio Access Network (RAN) perspective, including management architecture and functionalities as well as Service Level Agreement aspects impacting on the way that the shared RAN is deployed and operated. Then, the implications of multi-tenancy on mobility control are analysed in order to delineate the impact on Radio Resource Management (RRM) and Self-Organizing Network (SON) functionalities as a result of the emergence of this novel business model., Peer Reviewed, Postprint (published version)

The new era of mobile communications is dictated by the user demand for robust and high speed connections, data hungry applications and seamless connectivity. Operators and researchers all over the world are challenged to fulfill these requirements by providing enhanced coverage, increased capacity and efficient usage of the scarce spectrum. The introduction of the fourth generation systems (4G), LTE and LTE-A, have set the initiative for a technology evolution that offers new possibilities and is able to satisfy the user requirements and overcome the imposed challenges. However, and despite the improvements brought by the LTE and LTE-A systems, there are certain constraints that still need to be surpassed. LTE for example adopts innovating technologies, such as Orthogonal Frequency Division Multiplexing Access (OFDMA) that improves the spectral efficiency and reduces the Intra-Cell Interference. Nevertheless, Inter-Cell Interference (ICI) remains a constraining factor that can degrade the system capacity and limit the overall performance of the network. On that respect, Inter-Cell Interference Coordination (ICIC) techniques are adopted with target the interference mitigation. One of the limitations of these techniques is that follow static configurations lacking of flexibility and adaptation on network changes. Moreover, LTE-A employs enhanced and new techniques and involves alternative strategies. A promising solution lies on the introduction of Heterogeneous Networks (HetNets), which are networks that include low power small cells under the already existing macro cellular network and exploit several other technologies, such as WiFi. HetNets can further improve the network capacity, enhance the coverage and provide higher speed data transfer. However, due to the heterogeneous nature of the network, traditional methods for the user association, resource allocation and interference mitigation may not always be suitable since their design was based on homogeneous dep, La nueva era de las comunicaciones móviles viene marcada por la demanda de los usuarios por conseguir conexiones robustas de alta velocidad que permitan soportar aplicaciones de datos de elevados requerimientos. El cumplimiento de estos requisitos conlleva la necesidad de mejorar la cobertura, incrementar la capacidad y utilizar el espectro eficientemente. La introducción de los sistemas de cuarta generación (4G), LTE y LTE-A, ha dado lugar a una tecnología que ofrece nuevas posibilidades y es capaz de satisfacer las necesidades de los usuarios y superar los retos impuestos. Sin embargo, y a pesar de las mejoras introducidas por estos sistemas, hay ciertas limitaciones que todavía tienen que ser superadas. LTE, por ejemplo, adopta tecnologías tales como OFDMA que mejora la eficiencia espectral y reduce la interferencia intracelular. Sin embargo, la interferencia intercelular (ICI) sigue siendo un factor limitante que puede degradar la capacidad del sistema y limitar el rendimiento global de la red. En ese sentido, se requieren técnicas de coordinación de interferencias intercelulares (ICIC) con el objetivo de mitigar dicha interferencia. Una de las limitaciones de estas técnicas es que siguen configuraciones estáticas que carecen de flexibilidad y capacidad de adaptación a los cambios de la red. Por otra parte, LTE-A introduce nuevas mejoras, como las redes heterogéneas (HetNets), que son redes que incluyen pequeñas células de baja potencia conjuntamente con la red macrocellular y también pueden explotar diferentes tecnologías, como WiFi. Las HetNets pueden mejorar aún más la capacidad de la red, mejorar la cobertura y facilitar la transferencia de datos de mayor velocidad. Sin embargo, debido a la naturaleza heterogénea de la red, los métodos tradicionales para la asociación de usuarios, asignación de recursos y reducción de la interferencia pueden no ser siempre adecuados, ya que su diseño se basó en despliegues homogéneos. En este sentido, es preciso introducir t, Postprint (published version)

Deliverable D13.3 del projecte europeu NEWCOM#, The report presents the outcome of the Joint Research Activities (JRA) of WP1.3 in the last year of the Newcom# project. The activities focus on the investigation of bandwidth and energy efficient techniques for current and emerging wireless systems. The JRAs are categorized in three Tasks: (i) the first deals with techniques for power efficiency and minimization at the transceiver and network level; (ii) the second deals with the handling of interference by appropriate low interference transmission techniques; (iii) the third is concentrated on Radio Resource Management (RRM) and Interference Management (IM) in selected scenarios, including HetNets and multi-tier networks., Peer Reviewed, Postprint (published version)

Heterogeneous Networks (HetNets) have been a crucial point in the evolution of mobile networks that boost the network performance with the addition of small cells. The use of Enhanced ICIC (eICIC) techniques such as Almost Blank Subframes (ABS) has been introduced in HetNets to protect the small cells from high interferences. However this is done at the expense of lower macrocell user capacities. In this respect, in this work we propose a solution that starts from the principles of ABS and exploits jointly the dimensions of frequency, power and time in order to balance the trade-off between interference mitigation on the small cells and capacity degradation in the macrocells. Comparisons against the classical ABS and other existing solutions show the efficiency of the proposed scheme with improvements in the user capacity that reach up to 26% in the considered scenarios. This is achieved without significant degradation of the performance observed by small cell users., Peer Reviewed, Postprint (published version)

The use of Long Term Evolution (LTE) in the unlicensed 5 GHz band, referred to as LTE-U, is a promising enhancement to increase the capacity of LTE networks and meet the requirements foreseen for future systems. Nevertheless, coexistence among several LTE-U and/or Wi-Fi systems in the same band is a key technical challenge to be resolved. In this context, this paper focuses on the channel selection functionality for LTE-U enabled cells to decide the most appropriate channel to use for downlink traffic offloading in the unlicensed band. A distributed Q-learning mechanism that exploits prior experience is proposed to support this functionality, thus enabling coexistence with other systems in a smart and efficient way. The behavior of the proposed approach is illustrated in an indoor scenario with small cells from two different operators. A fully decentralized approach, where the channel selection decision-making is performed independently by each small cell in the scenario, is considered to initially assess the potentials of the Q-learning solution. Promising results are obtained revealing that the throughput achieved by the proposed approach can be between 96% and 99% of the optimum ideal achievable throughput., Peer Reviewed, Postprint (published version)

The use of Long Term Evolution (LTE) in the unlicensed 5 GHz band, referred to as LTE-U, is a promising enhancement to increase the capacity of LTE networks and meet the requirements of future systems. This paper considers a Q-learning based Channel Selection strategy to decide the most appropriate channel to use for downlink traffic offloading in the unlicensed band as a mechanism to greatly facilitate the coexistence among several LTE-U and/or Wi-Fi systems in the same band. The focus is placed on analyzing the robustness of the proposed approach in front of non-stationary conditions in the wireless environment. Simulation results allow assessing quantitatively the capability of the proposed strategy to relearn proper solutions when changes in the environment occur. Furthermore, the analysis evaluates quantitatively how fast the learning process has to be compared to the variations in the environment in order to retain an LTE-U throughput performance very close to the optimum one., Peer Reviewed, Postprint (published version)

The highly demanding requirements envisaged for future 5G networks together with the required support of new customers from vertical industries (e.g. e-health, automotive, energy) pose a big challenge for operators in 5G on how to balance investments, user experience and profitability. There will be the need to revisit the actual methodologies of network planning and operation, fully exploiting cognitive capabilities that embrace knowledge and intelligence to achieve a proper understanding of the network usage in multiple dimensions. In this respect, this paper presents a vision on how these planning and operation processes can rely on the inclusion of Artificial Intelligence (AI) concepts that will allow devising models to characterize the impact of many correlated inputs on specific operator objectives and to drive decisions for different processes., Peer Reviewed, Postprint (published version)

Deliverable D11.2 del projecte europeu NEWCOM#, The report presents the Intermediate Results of N# JRAs on Performance Limits of Wireless Communications and highlights the fundamental issues that have been investigated by the WP1.1. The report illustrates the Joint Research Activities (JRAs) already identified during the first year of the project which are currently ongoing. For each activity there is a description, an illustration of the adherence and relevance with the identified fundamental open issues, a short presentation of the preliminary results, and a roadmap for the joint research work in the next year. Appendices for each JRA give technical details on the scientific activity in each JRA., Peer Reviewed, Preprint

Deliverable D13.1 del projecte europeu NEWCOM#, The report presents the current status in the research area of energy- and bandwidth-efficient communications and networking and highlights the fundamental issues still open for further investigation. Furthermore, the report presents the Joint Research Activities (JRAs) which will be performed within WP1.3. For each activity there is the description, the identification of the adherence with the identified fundamental open issues, a presentation of the initial results, and a roadmap for the planned joint research work in each topic., Preprint

Deliverable D13.2 del projecte europeu NEWCOM#, The report presents the status of the research work of the various Joint Research Activities (JRA) in WP1.3 and the results that were developed up to the second year of the project. For each activity there is a description, an illustration of the adherence to and relevance with the identified fundamental open issues, a short presentation of the main results, and a roadmap for the future joint research. In the Annex, for each JRA, the main technical details on specific scientific activities are described in detail., Peer Reviewed, Postprint (published version)

User demand for capacity and high data rate applications imposes the need for new technologies able to cope with these challenges. Fourth Generation cellular networks have set the initiative for a technology evolution that will surpass the constraints and provide better quality of service and improved performance. In this context, Heterogeneous Networks (HetNets) deployments, combining a variety of different cell sizes, are considered in the literature in order to enhance the coverage and capacity of cellular systems. However, they require enhanced techniques especially for the user-to-cell association, resource allocation and interference management processes. On that respect, in this work we present a novel scheme that exploits jointly the frequency, power and time dimensions for interference mitigation in order to balance the trade-off between interference reduction to small cell users and throughput degradation for macrocell users. Simulation results have shown that the proposed solution utilizes more efficiently the available resources compared to a conventional scheme and boosts the capacity up to 45%., Peer Reviewed, Postprint (published version)

The progressive deployment of cell sites in wireless networks to deal with the massive demand of wireless services experienced in the last years has led to a huge increase in energy consumption and associated operational expenditures for wireless network operators. As a result, significant research efforts are being recently devoted towards energy efficient wireless communications. The use of relay nodes that enhance coverage/capacity in wireless systems has been identified as a means to improve energy efficiency thanks to the associated reduction in transmit power. In this context, this paper presents the assessment of the energy savings that can be achieved by means of relaying in a wireless system. As a difference from prior works where the impact of relaying on energy efficiency is obtained as a result of multiple aggregated effects, the analysis performed in this paper will highlight, separately, the role played by each of the key elements influencing on the performance, such as the propagation and shadowing effects, the energy consumption model parameters and the influence of the bit rate and spectral efficiency., Peer Reviewed, Postprint (published version)

Fourth Generation (4G) cellular networks present a number of improvements in the overall network performance. However, and despite the advanced technologies that are being employed, Inter Cell Interference (ICI) remains a constraining factor. ICI Coordination techniques target the minimization of ICI and have gained ground in the literature. The introduction of dynamicity in these schemes results in even better bandwidth utilization and enhances the overall performance. In this work, we propose a distributed algorithm that performs dynamic channel allocation to mitigate the ICI in cellular scenarios applying Partial Frequency Reuse (PFR). In particular, the algorithm is based on a Gibbs Sampler mechanism that allows achieving an optimized performance. Simulation results have shown that the proposed solution reduces the network interference up to 13 dB with respect to classical PFR. In addition, benefits have also been observed in the user capacity, where our scheme achieves improvements of up to 43% in terms of average user capacity and up to 17% for the users located at the cell edge., Peer Reviewed, Postprint (published version)

El acceso a servicios de banda ancha móvil es fundamental para mejorar la eficiencia y efectividad de las comunicaciones de seguridad pública y emergencias. En este artículo se defiende que el modelo de comunicaciones actual, caracterizado por el uso de tecnologías dedicadas, redes dedicadas y espectro dedicado , no es válido para sustentar la necesaria evolución de los servicios y sistemas de comunicaciones utilizados hoy en día por las organizaciones PPDR (Public Protection and Disaster Relief). A tal efecto, en el artículo se establecen y desarrollan los tres principios clave que, en opinión de los autores, son fundamentales para posibilitar y cimentar dicha evolución: (1) aprovechamiento de las tecnologías del entorno comercial; (2) explotación de estrategias de compartición de infraestructura y redes; y (3) incorporación de principios de compartición de espectro entre PPDR y otras aplicaciones., Postprint (published version)