76 research outputs found
How user throughput depends on the traffic demand in large cellular networks
Little's law allows to express the mean user throughput in any region of the
network as the ratio of the mean traffic demand to the steady-state mean number
of users in this region. Corresponding statistics are usually collected in
operational networks for each cell. Using ergodic arguments and Palm theoretic
formalism, we show that the global mean user throughput in the network is equal
to the ratio of these two means in the steady state of the "typical cell".
Here, both means account for double averaging: over time and network geometry,
and can be related to the per-surface traffic demand, base-station density and
the spatial distribution of the SINR. This latter accounts for network
irregularities, shadowing and idling cells via cell-load equations. We validate
our approach comparing analytical and simulation results for Poisson network
model to real-network cell-measurements
A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals
Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility
Mobile and Wireless Communications
Mobile and Wireless Communications have been one of the major revolutions of the late twentieth century. We are witnessing a very fast growth in these technologies where mobile and wireless communications have become so ubiquitous in our society and indispensable for our daily lives. The relentless demand for higher data rates with better quality of services to comply with state-of-the art applications has revolutionized the wireless communication field and led to the emergence of new technologies such as Bluetooth, WiFi, Wimax, Ultra wideband, OFDMA. Moreover, the market tendency confirms that this revolution is not ready to stop in the foreseen future. Mobile and wireless communications applications cover diverse areas including entertainment, industrialist, biomedical, medicine, safety and security, and others, which definitely are improving our daily life. Wireless communication network is a multidisciplinary field addressing different aspects raging from theoretical analysis, system architecture design, and hardware and software implementations. While different new applications are requiring higher data rates and better quality of service and prolonging the mobile battery life, new development and advanced research studies and systems and circuits designs are necessary to keep pace with the market requirements. This book covers the most advanced research and development topics in mobile and wireless communication networks. It is divided into two parts with a total of thirty-four stand-alone chapters covering various areas of wireless communications of special topics including: physical layer and network layer, access methods and scheduling, techniques and technologies, antenna and amplifier design, integrated circuit design, applications and systems. These chapters present advanced novel and cutting-edge results and development related to wireless communication offering the readers the opportunity to enrich their knowledge in specific topics as well as to explore the whole field of rapidly emerging mobile and wireless networks. We hope that this book will be useful for students, researchers and practitioners in their research studies
LTE in unlicensed spectrum: indoor planning, performance evaluation, and coexistence with WiFi
The pursuit of more bandwidth and more efficient spectrum usage has led to consider the use of Long Term Evolution (LTE) technology in unlicensed spectrum, a concept particularly useful for indoor deployments. However, LTE must be modified in order to guarantee a fair coexistence with other systems, particularly WiFi.
There exist several coexistence methods, such as listen-before-talk (LBT), advanced channel selection, duty cycle, and variations of them. Research into unlicensed spectrum has focused into LTE Licensed Assisted Access (LAA) and LTE-Unlicensed (LTE-U), expected to be specified in 2016.
The contribution of this thesis is complementary to the current work, and is focused on coexistence from the perspective of network planning and radio access optimization. This is accomplished with a framework that yields optimized network topologies that maximize the benefits from the LTE deployment, fulfill coverage criteria, and minimize interference. The efficacy of the statistically optimized network topologies has also been validated by means of system level simulations
Aspects of capacity enhancement techniques in cellular networks
Frequency spectrum is the scarce resource. From mobile operatorâs point of view, efficient utilization of the radio resources is needed while providing maximum coverage, and ensuring good quality of service with minimal infrastructure. In high capacity demanding areas, multilayer networks with multiband and multi radio access technologies are deployed, in order to meet the capacity requirements. In his doctoral thesis, Usman Sheikh has proposed a âSmart Traffic Handlingâ strategy, which is based on userâs required service type and location. Smart traffic handling scheme efficiently utilizes the different layers of the network, balances the load among them, and improves the system capacity. Power resources at base station are also limited. Usman Sheikhâs proposed âPower Control Scheme for High Speed Downlink Packet Access (HSDPA) networkâ improves the cell edge user experience, while maintaining the fairness among the other users in a cell. With the help of a proposed power control scheme, a user far from the base station can also enjoy the better quality of service.
Generally, mobile operators use macro cells with wide beam antennas for wider coverage in the cell, but future capacity demands cannot be achieved by using only them. âHigher Order Sectorizationâ is one possible way to increase the system capacity. Usman Sheikh proposed new network layouts called âSnowflakeâ and âFlowerâ tessellations, for 6-sector and 12-sector sites, respectively. These tessellations can be used as a basis for making a nominal network plan for sites with higher order sectorization. These tessellations would be helpful for simulation purposes. Through his work, he has also tried to highlight the importance of deploying âAdaptive MIMO Switchingâ in Long Term Evolution (LTE) system, the fourth generation of wireless networks.
In future, the fifth generation of wireless networks is expected to offer thousand times more capacity compared to LTE. The novel concept of âSingle Path Multiple Access (SPMA)â given by Usman Sheikh is a revolutionary idea, and gives a possibility to increase the system capacity by a giant margin. SPMA can be considered as a right step towards 5G technology.
Usman Sheikhâs work is of high importance not only from mobile operatorâs point of view; rather his contributions to the scientific community will also lead to better user (customer) experience. His work will definitely benefit the mankind in utilizing the limited resources in an optimum and efficient way
Spectrum Policy and Management
This project provides an examination of the FCCâs policies towards spectrum reallocation. The project examines the National Broadband Plan and how the FCC has approached the goals described within it. The demand for broadband communications has increased dramatically in recent years and has resulted in a predicted spectrum deficit in the near future. In addition to a number of spectrum auctions and their winners the project examines how the redistribution of spectrum impacts the broadband community. The project also provides an examination of spectrum reallocation and policy in other countries, to provide a broader view of spectrum policy. Finally the project examines new spectrum technologies and spectrum usage policies to further examine how the USâs spectrum policies should evolve
Recommended from our members
Application priority framework for fixed mobile converged communication networks
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence in order to offer integrated broadband services. These systems will need to offer higher data transmission capacities and long battery life, which is the catalyst for an everincreasing variety of air interface technologies targeting local area to wide area connectivity. Current integrated industrial networks do not offer application aware context delivery and enhanced services for optimised networks. Application aware services provide value-added functionality to business applications by capturing, integrating, and consolidating intelligence about users and their endpoint devices from various points in the network. This thesis mainly intends to resolve the issues related to ubiquitous application aware service, fair allocation of radio access, reduced energy consumption and improved capacity. A technique that measures and evaluates the data rate demand to reduce application response time and queuing delay for multi radio interfaces is proposed. The technique overcomes the challenges of network integration, requiring no user intervention, saving battery life and selecting the radio access connection for the application requested by the end user. This study is split in two parts. The first contribution identifies some constraints of the services towards the application layer in terms of e.g. data rate and signal strength. The objectives are achieved by application controlled handover (ACH) mechanism in order to maintain acceptable data rate for real-time application services. It also looks into the impact of the radio link on the application and identifies elements and parameters like wireless link quality and handover that will influence the application type. It also identifies some enhanced traditional mechanisms such as distance controlled multihop and mesh topology required in order to support energy efficient multimedia applications. The second contribution unfolds an intelligent application priority assignment mechanism (IAPAM) for medical applications using wireless sensor networks. IAPAM proposes and evaluates a technique based on prioritising multiple virtual queues for the critical nature of medical data to improve instant transmission. Various mobility patterns (directed, controlled and random waypoint) has been investigated and compared by simulating IAPAM enabled mobile BWSN. The following topics have been studied, modelled, simulated and discussed in this thesis: 1. Application Controlled Handover (ACH) for multi radios over fibre 2. Power Controlled Scheme for mesh multi radios over fibre using ACH 3. IAPAM for Biomedical Wireless Sensor Networks (BWSN) and impact of mobility over IAPAM enabled BWSN. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in multi radios over fibre performance in terms of application response delay and power consumption by upto 75% and 15 % respectively, reduction in traffic loss by upto 53% and reduction in delay for real time application by more than 25% in some cases
Redes de nova geração e o serviço universal de telecomunicaçÔes em Portugal
Doutoramento em Engenharia EletrĂłnicaThis thesis addresses the issue of Universal Service for telecommunications in the context of the access networks of next generation. This work aims to contribute to the redefinition of the concept of universal telecommunications service focusing primarily on extending it to broadband services as economic and social development factor and taking into account the degree of dependence that currently, modern societies have for the different communication and information services. Complementarily it also intended to meet some of the challenges set out in the European 2020 agenda. Universal Service is defined here as access to a telecommunications network (with obligations in terms of type and quality of service for the operator), by of all citizens at any country's geographical location, with uniform and accessible price. The approach adopted is the State as a mentor for social equity, respectful of the liberalized market dynamics but also knowledgeable of the requirements of modern telecommunications services and its relationship with the different technologies available. The possibility of subsidizing is assumed. The Universal ServiceÂŽs provision is subject to open to all operators, which are assumed to possess other profitability businesses, than the Universal Service, using technologies similar to those prescribed for the respective Universal Service provision contest. Although the work has components of economic and financial analysis, the approach is the engineering point of view, looking for help to identify technical and organizational solutions which offer prospects for the dissemination and adoption of next generation network solutions. As a point of departure the work gives an overview on the state of the art access networks , trying to identify which of the differences between this reality and possible scenarios for next-generation network with potential access to the generality of the people . The case of the Portuguese reality will be given special attention, taking into account their specific characteristics in terms of geography, demography, economics and market dynamics. The main results of this work are: âą Identification of possible scenarios for the evolution of existing networks, in particular in areas with deficit coverage. âą Identification of possible operating models and business to the materialization of the above scenarios developed and its economic analysis in an attempt to determine the critical factors associated with sustainability and / or need for subsidies. âą Contribution to the regulatory framework of new generation networks from the point of view of the constraints of technology and the specifics of the Universal Service.Esta tese aborda a questĂŁo do serviço universal de telecomunicaçÔes no contexto das redes de acesso de nova geração. Este trabalho pretende contribuir para a redefinição do conceito de Serviço Universal de TelecomunicaçÔes concentrando-se principalmente em estendĂȘ-lo a serviços de banda larga como factor de desenvolvimento econĂłmico e social e tendo em conta o grau de dependĂȘncia que, actualmente, as sociedades modernas tĂȘm em relação aos diferentes serviços de comunicação e informação. De forma complementar pretende-se tambĂ©m ir ao encontro de alguns dos desafios enunciados na Agenda Europeia 2020. Serviço Universal Ă© aqui definido como o acesso a uma rede de telecomunicaçÔes (com obrigaçÔes em termos de tipo e qualidade de serviço para o operador), por parte de todos os cidadĂŁos, em qualquer localização geogrĂĄfica do paĂs, a preços uniformes e acessĂveis. A perspectiva adoptada Ă© a Estatal como mentor da equidade social, respeitador das dinĂąmicas de mercado liberalizado mas tambĂ©m conhecedor dos requisitos dos modernos serviços de telecomunicaçÔes e da sua relação com as diferentes tecnologias disponĂveis. A possibilidade de subsidiação Ă© assumida. A prestação de Serviço Universal Ă© sujeita a concurso aberto a todos os operadores, que se assume possuĂrem outros negĂłcios, que nĂŁo apenas o Serviço Universal, com rentabilidade e usando tecnologias semelhantes Ă s preconizadas para a respectiva prestação de Serviço Universal. Embora o trabalho desenvolvido tenha componentes de anĂĄlise econĂłmico-financeira, a abordagem utilizada Ă© a de engenharia, procurando contribuir para a identificação de soluçÔes tĂ©cnicas e organizacionais que possam oferecer perspectivas sustentĂĄveis para a disseminação e adopção das soluçÔes redes de nova geração. Como ponto de partida o trabalho apresenta uma visĂŁo geral sobre o estado da arte das redes de acesso, procurando identificar quais os diferenciais existentes entre essa realidade e a de possĂveis cenĂĄrios de rede de prĂłxima geração com potencial de acesso para a generalidade dos cidadĂŁos. O caso da realidade Portuguesa serĂĄ objecto de uma atenção especial, tendo em consideração as suas especificidades em termos de geografia, demografia, economia e dinĂąmicas do mercado. Os principais resultados deste trabalho sĂŁo os seguintes: âą Identificação de possĂveis cenĂĄrios para a evolução das redes actuais, nomeadamente em ĂĄreas com deficit de cobertura de rede. âą Identificação de possĂveis modelos de operação e negĂłcio para a materialização dos cenĂĄrios acima desenvolvidos e respectiva anĂĄlise econĂłmica, como tentativa de determinar os factores crĂticos associados Ă sua sustentabilidade e /ou necessidade de subsidiação. âą Contributo para o quadro regulatĂłrio das Redes de Nova Geração sob o ponto de vista dos constrangimentos das tecnologias e das especificidades do Serviço Universal
Research on Reliable Low-Power Wide-Area Communications Utilizing Multi-RAT LPWAN Technologies for IoT Applications
PĆedklĂĄdanĂĄ disertaÄnĂ prĂĄce je zamÄĆena na âVĂœzkum spolehlivĂ© komunikace pro IoT aplikace v bezdrĂĄtovĂœch sĂtĂch vyuĆŸĂvajĂcĂch technologie Multi-RAT LPWANâ. Navzdory znaÄnĂ©mu pokroku v oblasti vĂœvoje LPWA technologiĂ umoĆŸĆujĂcĂ masivnĂ komunikace mezi zaĆĂzenĂmi (mMTC), nemusĂ tyto technologie vĂœkonnostnÄ dostaÄovat pro novÄ vznikajĂcĂ aplikace internetu vÄcĂ. HlavnĂm cĂlem tĂ©to disertaÄnĂ prĂĄce je proto nalezenĂ a vyhodnocenĂ limitĆŻ souÄasnĂœch LPWA technologiĂ. Na zĂĄkladÄ tÄchto dat jsou nevrĆŸeny novĂ© mechanismy umoĆŸĆujĂcĂ snazĆĄĂ plĂĄnovĂĄnĂ a vyhodnocovĂĄnĂ sĂĆ„ovĂ©ho pokrytĂ. NavrĆŸenĂ© nĂĄstroje jsou vyladÄny a validovĂĄny s vyuĆŸitĂm dat zĂskanĂœch z rozsĂĄhlĂœch mÄĆĂcĂch kampanĂch provedenĂœch v zĂĄkaznickĂœch LPWA sĂtĂch. Tato disertaÄnĂ prĂĄce dĂĄle obsahuje nĂĄvrh LPWA zaĆĂzenĂ vybavenĂœch vĂce komunikaÄnĂmi rozhranĂmi (multi-RAT) kterĂ© mohou umoĆŸnit pĆekonĂĄnĂ vĂœkonnostnĂch limitĆŻ jednotlivĂœch LPWA technologiĂ. SouÄasnĂĄ implementace se zamÄĆuje zejmĂ©na na snĂĆŸenĂ spotĆeby zaĆĂzenĂ s vĂce rĂĄdiovĂœmi rozhranĂmi, coĆŸ je jejich nejvÄtĆĄĂ nevĂœhodou. K tomuto ĂșÄelu je vyuĆŸito algoritmĆŻ strojovĂ©ho uÄenĂ, kterĂ© jsou schopnĂ© dynamicky vybĂrat nejvhodnÄjĆĄĂ rozhranĂ k pĆenosu.This doctoral thesis addresses the âResearch on Reliable Low-Power Wide-Area Communications Utilizing Multi-RAT LPWAN Technologies for IoT Applicationsâ. Despite the immense progress in massive Machine-Type Communication (mMTC) technology enablers such as Low-Power Wide-Area (LPWA) networks, their performance does not have to satisfy the requirements of novelty Internet of Things (IoT) applications. The main goal of this Ph.D. work is to explore and evaluate the limitations of current LPWA technologies and propose novel mechanisms facilitating coverage planning and assessment. Proposed frameworks are fine-tuned and cross-validated by the extensive measurement campaigns conducted in public LPWA networks. This doctoral thesis further introduces the novelty approach of multi-RAT LPWA devices to overcome the performance limitation of individual LPWA technologies. The current implementation primarily focuses on diminishing the greatest multi-RAT solutions disadvantage, i.e., increased power consumption by employing a machine learning approach to radio interface selection.
Flexible Application-Layer Multicast in Heterogeneous Networks
This work develops a set of peer-to-peer-based protocols and extensions in order to provide Internet-wide group communication. The focus is put to the question how different access technologies can be integrated in order to face the growing traffic load problem. Thereby, protocols are developed that allow autonomous adaptation to the current network situation on the one hand and the integration of WiFi domains where applicable on the other hand
- âŠ