Search

Network slicing enables multiple virtual networks to be instantiated and customized to meet heterogeneous use case requirements over 5G and beyond network deployments. However, most of the solutions available today face scalability issues when considering many slices, due to centralized controllers requiring a holistic view of the resource availability and consumption over different networking domains. In order to tackle this challenge, we design a hierarchical architecture to manage network slices resources in a federated manner. Driven by the rapid evolution of deep reinforcement learning (DRL) schemes and the Open RAN (O-RAN) paradigm, we propose a set of traffic-aware local decision agents (DAs) dynamically placed in the radio access network (RAN). These federated decision entities tailor their resource allocation policy according to the long-term dynamics of the underlying traffic, defining specialized clusters that enable faster training and communication overhead reduction. Indeed, aided by a traffic-aware agent selection algorithm, our proposed Federated DRL approach provides higher resource efficiency than benchmark solutions by quickly reacting to end-user mobility patterns and reducing costly interactions with centralized controllers., Comment: 15 pages, 15 Figures, accepted for publication at IEEE TVT

The Internet has been a valuable resource for many indigenous groups as a vehicle for self-representation. In this paper, we describe how the installation of a Wi-Fi signal in a Guaraní community in Greater Buenos Aires—as part of the community leader’s decolonizing media projects—generated issues within the community. While much indigenous media research concerns the politics of cultural representation, we consider the politics of everyday, intracommunity mobile communication practices. Firstly, our findings show how the choice of communication medium can become a political issue. An upsurge in mobile-mediated communication within the community contributed to the decline of face-to-face deliberations, which were the mainstay of communal sharing arrangements and which held a central position in understandings of Guaraní culture. Secondly, our findings show how discrepancies between users’ communication preferences and the readily available mobile media services can generate a use barrier by deterring users from obtaining the skills needed to effectively appropriate or transform mobile media services. Familiarity with a few mainstream social media apps not only reinforced imaginaries of the Internet as a nonindigenous space but also generated set ideas of what the Internet supports in terms of communicative form—social networking—and content type—mainstream media. In the end, the community leader’s decolonizing projects, aimed at using social media for community media dissemination, were not only rejected by community members but also undermined by the dynamics of mobile media practices in the community. We argue that limited mobile technology skills combined with commercially oriented mobile media services can hinder creative and adaptable mobile media practices, and in turn, undermine decolonizing mobile appropriations.

We analyze the role of bank mergers as determinants of the evolution of branch presence at the county level. Panel regressions based on county-level branch density are used to study differences across urban versus rural counties as well as pre- and post-crisis. The results indicate that bank mergers contributed to the increase of branches in the pre-crisis period and to its reduction in the post-crisis period, but the expansion effect of the mergers before the crisis mainly took place in metropolitan counties. Additional results show that broadband penetration has contributed to the reduction in the number of branches after the crisis and that branch closures are associated with an increase in the share of unbanked and underbanked households at the county level.

[eng] In the continuous evolution of mobile communication systems, there are many issues and aspects to be addressed, as well as in their effective implementation and deployment on cellular networks. In a general way, the most outstanding challenge is how to take the most advantage from the available resources, namely RF spectrum, to satisfy the communication requirements associated to a specific service or application offered to an end user. Energy efficiency has also become one important aspect associated to such requirements, since it has a significant practical impact on operators, namely regarding their networks operational expenditure, as well as on UEs, concerning their battery duration and associated autonomy. This thesis addresses and targets contributing to the growing concerns regarding energy efficiency in the ICT industry, specifically focusing on cellular wireless networks. Moreover, taking into account the current panorama and developments in this field, namely concerning the emerging 5G communication systems and networks, the heterogeneous network (HetNet) concept is also at the core of the work that has been carried out and is presented in this thesis. The work takes into consideration the two ends of the considered system of networks. The first are the nomad end users that should be able to roam freely in such system, always with continuous service provided in a seamless way, and the second is the core network managed by the respective telecommunications operator. To achieve this, the work carried out focused in addressing two key challenges in HetNets in general, specifically towards optimizing the energy efficiency associated to vertical handovers (VHO) and to radio resource management (RRM) mechanisms and approaches to allow energy efficient communication in a HetNet. The work addresses energy efficiency in two different perspectives, each using a different solution exploiting distinct available mechanisms specified for cellular wireless networks. One considers UEs integrating multiple RAT interfaces, and involve a VHO-based solution exploiting IEEE 802.21 standard, and the other targets both core and radio access networks, exploiting a RRM-based solution. The first proposed energy efficient solution exploiting features provided by IEEE 802.21 (MIH/MIIS) and VHO, targeting energy saving at modern multi-RAT mobile UEs, can eventually reduce the energy consumption at their RAT interfaces by roughly 30% on average, with a straightforward implementation, according to the attained simulation results. However, the currently proposed scheme presents a trade-off in terms of added packet loss linked to UEs velocity, which is mostly caused by delayed network re-association. In the second solution, for downlink OFDMA HetNet system, the proposed energy efficiency optimization algorithm for radio resource allocation, taking a given data rate requirement into account, associated to QoS, presented fast convergence, which is key in the design of real EE HetNet systems. The algorithm considers not only the radiated power, but also both types of the circuit power. Simulation results can eventually be exploited towards designing optimal energy consumption networks based on QoS-oriented HetNet method, while total power is fixed. As future work it would also be important to take into account the paradigm shift that arise with the emergence of new standards, namely 3GPP Release 15, placing the stepping stones for 5G systems and networks. In this perspective, at a first instance, it is key to go beyond the assumptions made in this work, by considering C-RAN architecture in the addressed challenge for achieving higher EE, which is a prime concern when redesigning existing and future mobile communication systems, namely in sustainable and environmental perspectives., [spa] La continua y rápida evolución de los sistemas de comunicación actuales presenta diversas líneas de actuación, con aspectos muy diversos como el despliegue e implementación eficiente de redes celulares. En este ámbito, el mayor desafío se presenta en cómo aprovechar los recursos disponibles, principalmente en cuanto al espectro RF, para satisfacer los requisitos asociados a los servicios o aplicaciones específicas ofrecidas al usuario final. La eficiencia energética también se ha convertido en un aspecto importante, dentro de los mencionados requisitos, debido al impacto que tiene para los operadores con respecto al coste operacional de las redes, y para el usuario final, debido al efecto en la autonomía de los dispositivos móviles. Este trabajo aborda la eficiencia energética en dos perspectivas diferentes, cada una utilizando una solución diferente que explota los distintos mecanismos disponibles especificados de las redes inalámbricas celulares, en particular HetNets. Uno considera que los dispositivos móviles integran múltiples interfaces RAT e involucran una solución basada en VHO que explota el estándar IEEE 802.21, y el otro apunta a las redes de acceso radio y núcleo de red, explotando una solución basada en RRM. La primera solución de eficiencia energética propuesta aprovecha las características proporcionadas por IEEE 802.21 (MIH / MIIS) y VHO para obtener un ahorro de energía en los dispositivos móviles modernos multi-RAT, y puede eventualmente reducir el consumo de energía en sus interfaces RAT en aproximadamente un 30% en promedio, con una sencilla implementación, de acuerdo con los resultados de la simulación. En la segunda solución, para el sistema OFDMA HetNet de enlace descendente, el algoritmo de optimización de eficiencia energética propuesto para la asignación de recursos de radio, teniendo en cuenta un dado requisito de velocidad de datos, asociado a QoS, presentó una convergencia rápida, lo cual es clave en el diseño de sistemas EE HetNet. El algoritmo considera no solo la potencia radiada, sino también los dos tipos de potencia del circuito. Los resultados de la simulación pueden aprovecharse para diseñar redes de consumo de energía óptimas basadas en el método HetNet orientado a QoS con una potencia total fija.

This paper analyzes mobile broadband plan prices in 37 countries between 2011 and 2014. Mobile network operators typically commercialize usage-based plans that include an access fee, a usage allowance (number of GB included in the tariff plan), and a penalty system should consumers exceed the contracted allowance. Our empirical model shows that the prices of these plans are lower than those of unlimited contracts, and that they depend on the type of penalty that is used. The prices also reflect service characteristics, including the technology provided, the download speed, and telephone call allowances. Plans that bundle mobile broadband plans with smartphone devices have longer contract duration and may be more expensive than plans that only include a SIM card. Specifically, broadband service plans are priced higher when they include an iPhone or a Samsung smartphone. The paper also discusses the impact of market structure and entry regulation on prices.

[spa] Esta Tesis doctoral presentará una reflexión teórico-crítica sobre el arte participativo que utiliza los dispositivos móviles de comunicación, dentro de un contexto marcado por redes de información monopolizadas por los poderes fácticos. La importancia de este análisis reside en la suposición de que el dominio gubernamental y corporativo sobre las estructuras informacionales restringe la eficacia de la participación artística. La interferencia de los gobiernos y de las corporaciones sobre las estructuras informáticas de comunicación podrían limitar las capacidades participativas —disminuiría el compromiso colectivo y debilitaría el espíritu de colaboración. Igualmente, la intervención de las fuerzas estatales y mercantiles sobre las redes de información podría frenar la adquisición de conocimientos, el desarrollo del sentido artístico y el fomento de intercambios sociales. Esta investigación presume que los principales responsables por dificultar los procesos participativos artísticos son: la vigilancia electrónica, el acopio de datos informáticos, el filtraje y el manejo de informaciones digitales. Todas estas prácticas serían realizadas tanto por los gobiernos como por las empresas. Además de suponer que la supremacía del poder público y comercial sobre el funcionamiento de las redes informáticas debilita la participación, este trabajo también quiere plantear soluciones para las problemáticas propuestas. El objetivo es enseñar que existen maneras de promover proyectos artísticos participativos eficientes, a través de la tecnología móvil. Para sustentar esta afirmación, presentaremos como recursos viables para solucionar los obstáculos enfrentados por las propuestas participativas: el uso de la tecnología libre y la práctica del “Sousveillance”. También sugeriremos la aplicación de los conceptos de las burbujas digitales y paredes virtuales, para la protección contra la vigilancia electrónica. Finalmente recomendaremos el empleo de los parámetros de la Estética Relacional creada por Nicolás Bourriaud, como ideología para las prácticas participativas con tecnología móvil. Esta Tesis lanza la hipótesis de que la Estética Relacional también debe ser aplicada a los proyectos participativos con dispositivos móviles. Además, cree que empleada conjuntamente a todas las sugerencias propuestas en el párrafo anterior, la teoría relacional es capaz de pro- mocionar una participación satisfactoria y eficiente. Aunque las ideas de Bourriaud presenten resistencias en relación a las prácticas artísticas realizadas a través de las nuevas tecnologías, su filosofía es generosa en relación a la participación artística. Por este motivo, es posible suponer que la Estética Relacional también puede representar una solución a las trabas enfrentadas por el arte participativo con la tecnología móvil. De esta manera, presumimos que los ideales relacionales asociados al arte participativo con dispositivos móviles pueden fomentar el encuentro, el intercambio, el espíritu colectivo, la ganancia del conocimiento y el desarrollo del sentido artístico.

Treballs Finals del Grau de d'Administració i Direcció d'Empreses, Facultat d'Economia i Empresa, Universitat de Barcelona, Curs: 2014-2015 , Tutor: Enrique Fuentes Moreno, El món de les aplicacions mòbils està en creixement. Des de l’aparició dels “smartphones” la creació d’aplicacions ha augmentat enormement, fins a considerar-se imprescindible per a moltes empreses el disposar d'una pròpia. Aquest projecte va encaminat a crear una empresa, que desenvoluparà una aplicació especifica, per tal de cobrir una necessitat en el sector del turisme e intentar causar un impacte significatiu dins de l’extens mon de les aplicacions mòbils. També aconseguir ser una empresa rentable a llarg termini. Els potencials clients són molts, ja que un gran nombre de persones disposa actualment de “smartphones”. Caldrà un bon plantejament de l’estratègia comercial a seguir, per tal de triomfar en un mercat en el que l’índex de èxit es molt baix. Durant el projecte analitzaré les característiques dels possibles clients, els competidors, directes e indirectes i les opcions de creixement de l’aplicació en cas de tenir èxit, ja que l’objectiu es crear una aplicació líder en el sector turisme, la qual es segueixi desenvolupant i creixent dia a dia.

Servitization is still currently under analysis by the literature regarding the incorporation of services in manufacturing companies in order to create value. Although traditionally companies offered services related to its products, especially guarantees and maintenance, new trends associated to the servitization process has provided these services to a much greater significance as generating added value for the customer.

Treballs Finals de Grau d'Enginyeria Informàtica, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2013, Director: Simone Balocco, On this report is described in what the stitching technique consist of, which the state of art on stitching methods is and how this technique has been recently assimilated by mobile devices market. This report also includes a full description of the developed applications which allow stitching images from pictures taken by an Android device. The first application is an Android application. The second application is a Java server. The development, the installation, the management and configuration of the Android app and the service have been detailed in order to provide a correct understanding of the work done. Both applications are detailed by several diagrams and explanations, which represent its internal design and how they have been implemented.

Ambient intelligence is going to focus the next advances in wireless technologies. Hence, the increasing demand on radio frequency (RF) devices and applications represents, not only a challenge for technological industries to improve its roadmaps, but also for RF engineers to design more robust, low-power, small-size and low-cost devices. Regarding to communication robustness, in the latest years, differential topologies have acquired an important relevance because of its natural noise and interference immunity. Within this framework, a differential n-port device can still be treated with the classical analysis circuit theory by means of Z-,Y-, h-parameters or the most suitable S-parameters in the radio frequency field. Despite of it, Bockelman introduced the mixed-mode scattering parameters, which more properly express the differential and common-mode behavior of symmetrical devices. Since then, such parameters have been used with a varying degree of success, as it will be shown, mainly because of a misinterpretation. Thereby, this thesis is devoted to extend the theory of mixed-mode scattering parameters and proposes the methodology to analyze such devices. For this proposal, the simplest case of a two-port device is developed. By solving this simple case, most of the lacks of the current theory are filled up. As instance, it allows the characterization and comparison of symmetric and spiral inductors, which have remained a controversy point until now. After solving this case, the theory is extended to a n-port device. Another key point on the fast and inexpensive development of radio frequency devices is the advance on fast CAD tools for the analysis and synthesis of passive devices. In the case of silicon technologies, planar inductors have become the most popular shapes because of its integrability. However, the design of inductors entails a deep experience and acknowledge not only on the behavior of such devices but on the use of electromagnetic (EM) simulators. Unfortunately, the use of EM simulators consumes an important quantity of time and resources. Thereby, this thesis is devoted to improve some of the aspects that slow down the synthesis process of inductors. Therefore, an ‘ab initio’ technique for the meshing of planar radio frequency and microwave circuits is described. The technique presented can evaluate the losses in the component with a high accuracy just in few seconds where an electromagnetic simulator would normally last hours. Likewise, a simple bisection algorithm for the synthesis of compact planar inductors is presented. It is based on a set of heuristic rules obtained from the study of the electromagnetic behavior of these planar devices. Additionally, design of a single-ended to differential low noise amplifier (LNA) in a CMOS technology is performed by using the methods and tools described., L'enginyeria de radiofreqüència i la tecnologia de microones han assolit un desenvolupament inimaginable i avui en dia formen part de la majoria de les nostres activitats diàries. Probablement, la tecnologia mòbil ha tingut un desenvolupament més ràpid que qualsevol altre avenç tecnològic de l'era digital. Avui en dia, podem dir que el paradigma de la mobilitat s'ha assolit i tenim accés ràpid a internet des de qualsevol lloc on podem estar amb un dispositiu de butxaca. No obstant això, encara hi ha fites per endavant. Es més que probable que el paradigma de l’ "ambient intelligence” sigui el centre dels pròxims avenços en les tecnologies sense fils. A diferencia del paradigma de l"ambient intelligence', l'evolució de la tecnologia de la informació mai ha tingut l'objectiu explícit de canviar la societat, sinó que ho van fer com un efecte secundari, en canvi, les visions d' “ambient intelligence” proposen expressament el transformar la societat mitjançant la connexió completa i la seva informatització. Per tant, l'augment de la demanda de dispositius de ràdio freqüència (RF) i de les seves possibles aplicacions representa, no només un repte per a les indústries tecnològiques per millorar els seus plans de treball, sinó també per als enginyers de RF que hauran de dissenyar dispositius de baixa potència, més robusts, de mida petita i de baix cost. Quant a la robustesa dels dispositius, en els últims anys, les topologies de tipus diferencial han adquirit una important rellevància per la seva immunitat natural al soroll i resistència a les interferències. Dins d'aquest marc, un dispositiu de nports diferencial, encara pot ser tractat com un dispositiu 2nx2n i la teoria clàssica d'anàlisi de circuits (és a dir, la temia de quadripols) es pot aplicar a través de paràmetres Z, Y, h o els paràmetres S, més adequats en el camp de freqüència de ràdio. Tot i això, Bockelman i Eisenstadt introdueixen els paràmetres S mixtos, que expressen més adequadament el comportament diferencial i en mode comú de dispositius simètrics o asimètrics. Des de llavors, aquests paràmetres s'han utilitzat amb un grau variable d'èxit, com es mostrarà, principalment a causa d'una mala interpretació. D'aquesta manera, la primera part d'aquesta tesi està dedicada a estendre la teoria dels paràmetres S de mode mixt i proposa la metodologia d'anàlisi d'aquest tipus de dispositius i circuits. D'aquesta forma, en el Capítol 2, es desenvolupa el cas més simple d'un dispositiu de dos ports. En resoldre aquest cas simple, la major part de les mancances de la teoria actual es posen de relleu. Com a exemple, pennet la caracterització i la comparació de bobines simètriques i espiral no simètriques, que han estat un punt de controvèrsia fins ara. Després de resoldre aquest cas, al Capítol 3 s'estén la teOIia a un dispositiu de n-ports dels quals un nombre pot ser single-ended i la resta diferencials. És en aquest moment quan la dualitat existent entre els paràmetres S estàndard i de mode mixt es pot veure clarament i es destaca en el seu conjunt. Aquesta teoria permet, tanmateix, estendre la teoria clàssica d'amplificadors quan s'analitzen per mitjà de paràmetres S. Un altre punt clau en el desenvolupament ràpid i de baix cost dels dispositius de radiofreqüència és l'avenç en les eines CAD ràpides per a l'anàlisi i síntesi dels dispositius passius, en especial dels inductors. Aquests dispositius apareixen tot sovint en el disseny de radio freqüència degut a la seva gran versatilitat. Tot i que hi ha hagut múltiples intents de reemplaçar amb components externs o circuits, fins i tot actius, en el cas de les tecnologies de silici, els inductors planars s'han convertit en les formes més populars per la seva integrabilitat. No obstant això, el disseny d'inductors implica conèixer i posseir una experiència profunda no només en el comportament d'aquests dispositius, però també en l'ús de simuladors electromagnètics (EM). Desafortunadament, l'ús dels simuladors EM consumeix una quantitat important de temps i recursos. Per tant, la síntesi dels inductors representa un important inconvenient actualment. D'aquesta manera, la segona part d'aquesta tesi està dedicada a millorar alguns dels aspectes que frenen el procés de síntesi dels inductors. Per tant, en el Capítol 4, es descriu una tècnica 'ab initio' de generació de la malla per bobines planars en ràdio freqüència i microones. La tècnica es basa en l'estudi analític dels fenòmens d'aglomeració de corrent que tenen lloc a l'interior del component. En aquesta avaluació, no es requereix una solució explícita dels corrents i de les càrregues arreu del circuit. Llavors, el nombre de cel•les de la malla assignades a una tira de metall donada, depèn del valor inicialment obtingut a partir de l'estudi analític. La tècnica presentada pot avaluar les pèrdues en el component amb una gran precisió només en uns pocs segons, quan comparat amb un simulador electromagnètic normalment es necessitaria hores. De la mateixa manera, en el Capítol 5 es presenta un senzill algoritme de bisecció per a la síntesi d'inductors planars compactes. Es basa en un conjunt de regles heurístiques obtingut a partir de l'estudi del comportament electromagnètic d'aquests dispositius planars. D'aquesta manera, el nombre d'iteracions es manté moderadament baix.D'altra banda, per tal d'accelerar l'anàlisi en cada pas, s'utilitza un simulador ràpid electromagnètic planar, el qual es basa en el coneixement que es té del component sintetitzat. Finalment, en el Capítol 6, la metodologia de paràmetres S de mode mixt proposada i les eines CAD introduides s'utilitzen àmpliament en el disseny d'un amplificador de baix soroll “single-ended” a diferencial (LNA), mitjançant una tecnologia estàndard CMOS.L'amplificador de baix soroll és un dels components claus en un sistema de recepció de radio freqüència, ja que tendeix a dominar la sensibilitat i la figura de soroll (NF) de tot el sistema. D'altra banda, les característiques d'aquest circuit estan directament relacionades amb els components actius i passius disponibles en una tecnologia donada. Per tant, la tecnologia escollida, el factor de qualitat dels passius, i la forma com es caracteritzen tindran un alt impacte en les principals figures de mèrit del circuit real.

Energy conservation is a critical issue regarding wireless mobile ad hoc networks, since the nodes are battery restrained and the depletion of their power defines the lifetime of the network. In this work a mechanism for energy saving and timely delivery of data packets is incorporated into the route discovery phase to select paths with lower cost. The proposed algorithm utilizes two metrics: residual energy and queue length at each node. Buffer information is considered as a traffic load characteristic and its use is twofold: limitation of battery power consumption and end-to-end delay. A simulation-based performance comparison between a routing ad hoc protocol and its modified energy and delay-constrained version demonstrates that the latter one improves system performance for certain network scenarios.

In this paper, an inhibit sense multiple access–direct sequence/code division multiple access (ISMA-DS/CDMA) medium access control protocol for a packet transmission mobile radio network is presented. The main feature of this protocol is its ability to retain the inherent flexibility of random access protocols while at the same time reducing to some extent the randomness in the access in order to increase the system capacity. In this framework, the protocol is presented together with some adaptive mechanisms that improve the protocol performance by means of regulating the access and varying the transmission bit rate according to the channel load that is broadcast by the base station. As a result, an adaptive bit rate algorithm is presented that reaches a throughput value close to the theoretical maximum.

Code-division multiple-access (CDMA) schemes appear to be very promising access techniques for coping with the requirements of third-generation mobile systems, mainly because of their flexibility. This paper proposes an adaptive S-ALOHA DS-CDMA access scheme as a method for integrating nonreal-time (i.e., Internet applications) and real-time (i.e., voice) services in a multicell scenario by exploiting the potentials of CDMA under time-varying channel load conditions. The adaptive component makes data terminals autonomously change their transmission rate according to the total (voice+data) channel occupancy, so that the minimum possible data delay, which can be analytically obtained by defining a birth-death process, is almost always achieved. Moreover, by means of a simplified cellular model, the proposed algorithm revealed the same behavior, i.e., it tries to select the most suitable transmission rate at any time slot, when it is affected by intercell interference and even by power control imperfections. Finally, in order to gain more insight into the potentials of such an access strategy, the adaptive S-ALOHA CDMA scheme is then compared to a reservation time-division multiple-access (TDMA)-based protocol (PRMA++), showing the benefits of the CDMA-based solution in terms of capacity, flexibility, and data delay performance.

A new wide-band mobile channel emulator for the CODIT project is designed and implemented. The UMTS code-division testbed (CODIT R2020) is a research project within the European RACE-II program set up by the Commission of the European Community. Our goal is to be able to simulate in the laboratory, in real time, the multipath propagation found in the mobile radio channel. As code-division multiple access (CDMA) is the access technique within the CODIT project, it was realized that the channel emulator must have simultaneously good delay resolution between propagation paths and long duration of the impulse response. These considerations led to a very flexible channel emulator specifically designed to host the new wide-band channel models developed within the CODIT project. Our emulator features three independent inputs and two outputs, up to 20 complex propagation paths, 10-MHz radio frequency (RF) bandwidth, a delay resolution of 50 ns, and a maximum duration of the channel impulse response of 80 /spl mu/s. Starting with an explanation of the global structure of the new channel emulator, we derive the optimum design of the interpolation procedures and present the main implementation issues arising from our initial architecture. Finally, we report the results of the laboratory tests of the first prototype of the channel emulator.

Spatial diversity is an attractive technology to cope with the fading channel encountered in mobile communications. This paper presents novel closed analytical expressions of the bit-error rate (BER) achievable in a coherent binary phase-shift-keying (CBPSK) direct-sequence code-division multiple-access (DS/CDMA) system for any power delay profile and for either postdetection selection or maximal ratio combining (MRC). In particular, expressions for the cutoff rate Ro and for its related parameter D are also formulated in order to assess the system performance under the consideration of some channel coding schemes. Finally, an exemplary study is carried out in order to illustrate the behavior of a realistic space-diversity code-division multiple-access (CDMA) system according to the analytical expressions that have been derived

This paper presents a novel adaptive direct-sequence code-division multiple-access (DS-CDMA) slotted-ALOHA (S-ALOHA) packet random-access scheme with transmitter-based spreading codes for mobiles. It is aimed at improving throughput and message delay delivery when traffic load values below the saturation point of the conventional DS-CDMA S-ALOHA system are sensed in the channel. For this purpose, one mobile-station (MS) and two base-station (BS)-assisted algorithms are envisaged to control the change of the transmission rate according to the traffic load. These algorithms revealed that the optimum behavior, obtained using a Markov chain model, may almost be reached at a low-complexity cost. A traffic model based on a realistic statistical length distribution of the messages illustrates how the delay delivery can be greatly reduced with the proposed algorithms. Finally, the impact of forward-error-correction (FEC) coding on the adaptive system is also studied.

El proceso de servitizacion unido al desarrollo vertiginoso de las nuevas plataformas de dispositivos moviles esta constantemente evolucionando hacia el diseno y desarrollo de productos/servicios que responden practicamente de manera instantanea a las nuevas necesidades y deseos de los clientes. No obstante, tal proceso ha venido unido en el ambito de los dispositivos moviles al desarrollo de aplicaciones especificas tanto para plataformas abiertas como cerradas. Sin embargo, la evolucion tecnologica permite en la actualidad ofrecer servicios de caracter mas amplio a traves de las denominadas ROMs en plataformas abiertas. Este trabajo analiza los avances y las perspectivas futuras relativas a la estrategia de servitizacion asi como su evolucion, tendencias y vinculacion de la misma con el desarrollo de plataformas como via directa de comunicacion y colaboracion entre la empresa y el cliente.

In this paper, the bit error rate (BER) performance of predetection diversity trellis coded multilevel phase shift keying (TCM-MPSK) and postdetection diversity trellis coded multilevel differential phase shift keying (TCM-MDPSK), transmitted over a Rayleigh fading channel is presented. Novel analytical upper bounds using the transfer function bounding technique are obtained and illustrated by several numerical examples. A new asymptotically tight upper bound for the maximal ratio combining (MRC) diversity schemes is also derived. In order to analyze practical TCM schemes (four or more states), only trellis codes holding uniform error property (UEP) and uniform distance property (UDP) are considered, enabling the encoder transfer function to be obtained from a modified state transition diagram, having no more states than the encoder itself. Monte-Carlo simulation results, which are more indicative of the exact system performance, are also given.

Analytic expressions have been derived for the probability density functions of the total signal-to-interference ratio when considering mixed-type interference sources in the reverse link of a DS/CDMA packet radio system with Rayleigh fading. Four different scenarios were studied, and the corresponding expressions are presented for each situation. The users are divided into two groups: those that apply a closed-loop power control and those that only use an open-loop power control. By making use of these expressions, the mean block error probability is derived as a function of the number of total interfering users in each group.

In the context of third-generation (3G) systems a mix of services with different requirements are expected. Consequently, packet scheduling mechanisms for quality of service (QoS) guarantees will play a key role. This paper proposes a new scheduling strategy that makes consistent the target quality in the radio link with the priority level assigned to each user. The performance of such a strategy is assessed by system level simulations and, in order to gain more insight into the difficulties of this optimization problem, it is compared to other alternatives. This work is part of the Wineglass project, within the Fifth Framework Program of the European Commission (IST), where a real time demonstrator including the radio resource management tasks is being developed. Thus, an implementation approach of the proposed scheduling is also described. The implementation is based on lookup tables and this approach is validated by simulation.

La Servitización está siendo en la actualidad objeto de análisis por parte de la literatura especializada en la medida en que trata la incorporación de servicios en empresas manufactureras con el fin de crear valor. Aunque tradicionalmente las empresas siempre han ofrecido servicios vinculados a sus productos, especialmente garantías y mantenimiento, las nuevas tendencias asociadas al proceso de servitización ha dotado a estos servicios de una significación mucho mayor como generadores de valor añadido para el cliente.

Together with the rapid development of new platforms for mobile devices, the servitization process is constantly evolving in the design and development of products and services that respond almost instantly to customers' changing needs and desires. In the field of mobile devices this process has been attached to the development of specific applications for both open and closed platforms. However, the advance of technology currently allows for the provision of broader services through open platforms in the form of ROMs. This paper analyzes the current developments in servitization strategy and proposes future directions it might take in the development of platforms as direct channels for companycustomer communication and collaboration. Keywords: servitization, globalisation, value creation, platforms, mobile devices

Previous studies have identified the rivalry among technological platforms as one of the main driving forces of broadband services penetration. This paper draws on data from the Spanish market between 2005 and 2011 to estimate the main determinants of broadband prices. Controlling for broadband tariffs features and network variables, we examine the impact of the different modes of competition on prices. We find that inter-platform competition has no significant effects over prices, while intra-platform competition is a key driver of the prices charged in the broadband market. Our analysis suggests that the impact of different types of competition on prices is critically affected by the levels of development of the broadband market achieved by the considered country

This paper presents and analyzes a new near-optimum medium access control (MAC) protocol. The proposed access scheme is suitable for a CDMA mobile communication environment, and keeps under control and upper bounded the number of simultaneous transmissions. It has a delay performance approaching that of an ideal optimum M/M/K system, where K is the number of spreading codes being used (maximum number of simultaneous transmissions). The protocol is a free random access protocol when the traffic load is light, and switches smoothly and automatically to a reservation protocol when traffic load becomes heavier. It is based on distributed queues and a collision resolution algorithm. Moreover, a physical receiver structure is proposed and analyzed in order to preserve the robustness of the protocol in a wireless link. The results obtained show that the protocol outperforms other well known medium access protocols in terms of stability and delay, even when taking into account the loss caused by channel propagation conditions.

A type II hybrid automatic repeat request scheme is considered as a retransmission strategy in a direct-sequence code-division multiple-access packet mobile radio network. An analysis based on equilibrium point analysis is presented to model the behavior of the system in a message-based traffic generation model. A simulation approach is introduced to validate the proposed analytical model, obtaining results that closely match those derived theoretically.

This paper analyzes the performance of blind equalization using the complex cepstrum of third-order moments applied to 4-QAM time division multiple access (TDMA) indoor radio communication systems. In particular, we have modeled a dispersive indoor channel with Rice statistics. We used the blind algorithms to estimate the channel-impulse response, and from this, we computed the equalizer coefficients using a classical minimum mean square error (MMSE) algorithm. In order to evaluate the system performance, we calculated the bit error rate (BER) of a decision feedback equalizer (DFE) that uses a tricepstrum algorithm to estimate the channel-impulse response. The results are compared with those obtained using a least sum of square errors (LSSE) algorithm as a channel estimator and considering the exact channel response. The results obtained show that this kind of blind equalizer performs better than the more classically trained equalizer when Rice channels with a strong direct path and signal-to-noise ratios (SNR’s) lower than 20 dB are taken into account. However, some problems relating to the length of time needed for convergence must be solved.

Code-division multiple-access (CDMA) schemes appear to be very promising access techniques for coping with the requirements of third-generation mobile systems, mainly because of their flexibility. This paper proposes an adaptive S-ALOHA DS-CDMA access scheme as a method for integrating nonreal-time (i.e., Internet applications) and real-time (i.e., voice) services in a multicell scenario by exploiting the potentials of CDMA under time-varying channel load conditions. The adaptive component makes data terminals autonomously change their transmission rate according to the total (voice+data) channel occupancy, so that the minimum possible data delay, which can be analytically obtained by defining a birth-death process, is almost always achieved. Moreover, by means of a simplified cellular model, the proposed algorithm revealed the same behavior, i.e., it tries to select the most suitable transmission rate at any time slot, when it is affected by intercell interference and even by power control imperfections. Finally, in order to gain more insight into the potentials of such an access strategy, the adaptive S-ALOHA CDMA scheme is then compared to a reservation time-division multiple-access (TDMA)-based protocol (PRMA++), showing the benefits of the CDMA-based solution in terms of capacity, flexibility, and data delay performance.

This paper presents a novel adaptive direct-sequence code-division multiple-access (DS-CDMA) slotted-ALOHA (S-ALOHA) packet random-access scheme with transmitter-based spreading codes for mobiles. It is aimed at improving throughput and message delay delivery when traffic load values below the saturation point of the conventional DS-CDMA S-ALOHA system are sensed in the channel. For this purpose, one mobile-station (MS) and two base-station (BS)-assisted algorithms are envisaged to control the change of the transmission rate according to the traffic load. These algorithms revealed that the optimum behavior, obtained using a Markov chain model, may almost be reached at a low-complexity cost. A traffic model based on a realistic statistical length distribution of the messages illustrates how the delay delivery can be greatly reduced with the proposed algorithms. Finally, the impact of forward-error-correction (FEC) coding on the adaptive system is also studied.