Deployment of Femtocells in 3rd Generation Networks

Femtosolulla tarkoitetaan pientä matkapuhelinverkon solua, jonka liitäntäyhteytenä operaattorin verkkoon käytetään kuluttajan omaa laajakaistaliittymää. Femtosolut ovat itsestään asentuvia eli niiden käyttöönottoon ei tarvita ammattitaitoisen asentajan erillistä käyntiä. Kooltaan femtosolut ovat nykyisten langattomien lähiverkkojen tukiasemien kokoisia. Kova kilpailu ja kuluttajien jatkuvat odotukset entistä nopeammista datayhteyksistä saavat laitevalmistajat jatkuvasti kehittelemään uusia, entistä edullisempia, ratkaisuja. 2100 MHz taajuudella toimiville 3G UMTS verkoille on ollut ongelmallista saavuttaa niin hyvää peittoa sisätiloissa ja haja-asutusalueilla, mihin asiakkaat ovat tottuneet toisen sukupolven matkapuhelinverkoissa. Femtosolut tarjoavat edullisen ja nopean tavan kapasiteetin ja peiton parantamiseen sekä koti että yritysympäristöissä. Ensimmäisiä laajamittaisia UMTS femtosolu verkkojan odotetaan toteutuvaksi jo vuoden 2009 aikana. Femtosoluja on aiemmin tutkittu lähinnä liiketoimintamallina sekä niiden tuomaa etua on simuloitu yksinkertaisina hyvin teoreettisina hahmotelmina. Tämän diplomityön tarkoituksena on tutkia femtosolujen käyttöönottoa nykyisten 3G verkkojen rinnalla ja siihen liittyviä mahdollisia ongelmia. Työssä tullaan esittelemään femtosolut tekniikkana ja 3GPP:n standardisoima femtosoluratkaisu Home NodeB. Lisäksi esitellään verkkoon tarvittavat lisäelementit ja femtosoluverkon erilaiset mahdolliset toteutustavat. Femtosolujen tehokkuutta tutkittiin simuloimalla olemassa olevaa ympäristöä kuvaavaa verkkoa. Simulointityökaluna käytettiin laajamittaisessa tuotantokäytössä olevaa kaupallista radioverkkosuunnittelutyökalua. Simulaatioiden tuloksina nähtiin peiton parantuvan femtosolujen ansioista kaikissa tilanteissa, sekä verkon kokonaiskapasiteetin jopa viisinkertaistuvan, femtosolujen ollessa omalla kanavallaan. Femtosolujen käyttöönotto ei merkittävästi huononna makroverkon suorituskykyä. Päinvastoin, huolellisesti suunniteltuna makroverkon suorituskyky voi jopa parantua. Simulaatiot eivät voi antaa vastausta kaikkiin mahdollisiin femtosolujen ongelmiin ja kokeiluprojektit ovat tarpeen.Femtocells are small mobile telecommunication network basestations using the customers' DSL or cable modem connections as backhaul. In addition, femtocells are self-configuring and do not require a professional for installation. The devices themselves are approximately of the same size as the current Wi-Fi access points. The growing capacity expectations and intensive competition between operators is constantly driving vendors to come up with new solutions. In 2100 MHz 3G UMTS networks, indoor and rural coverage are not at the level customers are used to with 2G networks. Femtocells are a cheap and fast way to offer capacity and coverage to homes and offices. First large scale UMTS femtocell implementations are predicted to happen during the year 2009. Many researchers have studied the femtocell business model, and simulated the performance and co-operation with the macro layer network. These studies, however, have been often done in a very theoretical honeyconb simulating environment. This thesis will study the possible problems in femtocell rollouts and evaluate the status of current standardization and available devices. The femtocell specified in 3GPP standards, known as the Home NodeB, and other new components needed to integrate the solution with the current networks are presented together with the different possible deployment configurations. Performance of femtocells was examined by simulations with a widely used radio network planning tool and simulator. The simulations studied service coverage and throughput. This thesis shows how the coverage is improved by femtocells and how the total network capacity gains can be up to 5 times, compared to the current macro layer network. This can be achieved with femtocells implemented on a dedicated carrier. Furthermore, it is shown how the femtocells do not cause serious problems to the macro network, on the contrary, by careful planning macro layer performance can even be enhanced. Nevertheless, everything can not be evaluated by simulations. Piloting is the next natural step to learn more about femtocell functionality

Interference Management Based on RT/nRT Traffic Classification for FFR-Aided Small Cell/Macrocell Heterogeneous Networks

Cellular networks are constantly lagging in terms of the bandwidth needed to support the growing high data rate demands. The system needs to efficiently allocate its frequency spectrum such that the spectrum utilization can be maximized while ensuring the quality of service (QoS) level. Owing to the coexistence of different types of traffic (e.g., real-time (RT) and non-real-time (nRT)) and different types of networks (e.g., small cell and macrocell), ensuring the QoS level for different types of users becomes a challenging issue in wireless networks. Fractional frequency reuse (FFR) is an effective approach for increasing spectrum utilization and reducing interference effects in orthogonal frequency division multiple access networks. In this paper, we propose a new FFR scheme in which bandwidth allocation is based on RT/nRT traffic classification. We consider the coexistence of small cells and macrocells. After applying FFR technique in macrocells, the remaining frequency bands are efficiently allocated among the small cells overlaid by a macrocell. In our proposed scheme, total frequency-band allocations for different macrocells are decided on the basis of the traffic intensity. The transmitted power levels for different frequency bands are controlled based on the level of interference from a nearby frequency band. Frequency bands with a lower level of interference are assigned to the RT traffic to ensure a higher QoS level for the RT traffic. RT traffic calls in macrocell networks are also given a higher priority compared with nRT traffic calls to ensure the low call-blocking rate. Performance analyses show significant improvement under the proposed scheme compared with conventional FFR schemes

Intereference Management in LTE-Advanced Heteogeneous Network

In this thesis, we consider the problem of interference management in heterogeneous networks which is one of the main features proposed in long term evolution advanced (LTE-Advanced)communications standard. The network architecture of heterogeneous network consists of a main cell coexisting with different types of smaller cells. Heterogeneous networks are one cost effective way of handling the unrelenting data traffic demand. The major technical challenge associated with this type of network architecture is the interference experienced between coexisting cells. Interference can be either between similar type of cells or between different types of cells within the network area. In this thesis, we consider a heterogeneous network with a macro cell coexisting with a femto cell. The interference between the cells will lower system performance and eventually result in poor macro user experience. Among the various enhanced intercell interference coordination (eICIC) techniques proposed in the third generation partnership project (3GPP), we focus on power control and time domain schemes using almost blank subframes (ABS). However,these interference management schemes reduce the throughput of femto cell users. This necessitates the need to optimize the resources of power and ABS transmission so that interference experienced by macro user is low and throughput of femto user is high simultaneously. Hence, we consider a joint optimization problem to find the optimal value of power and number of ABS transmission required at the femto cell. In previous work, these optimal parameters were obtained for a system with a macro base station (MBS) serving only one macro user in downlink. We extend the analysis to determine optimal parameters when MBS serves multiple macro users. Specifically, we show that the optimal parameters of power and number of ABS transmissions obtained for the macro user closest to the femto base station (FBS)guarantees maximum throughput for the femto user and minimal interference for all other macro users

Optimization of Mobility Parameters using Fuzzy Logic and Reinforcement Learning in Self-Organizing Networks

In this thesis, several optimization techniques for next-generation wireless networks are proposed to solve different problems in the field of Self-Organizing Networks and heterogeneous networks. The common basis of these problems is that network parameters are automatically tuned to deal with the specific problem. As the set of network parameters is extremely large, this work mainly focuses on parameters involved in mobility management. In addition, the proposed self-tuning schemes are based on Fuzzy Logic Controllers (FLC), whose potential lies in the capability to express the knowledge in a similar way to the human perception and reasoning. In addition, in those cases in which a mathematical approach has been required to optimize the behavior of the FLC, the selected solution has been Reinforcement Learning, since this methodology is especially appropriate for learning from interaction, which becomes essential in complex systems such as wireless networks. Taking this into account, firstly, a new Mobility Load Balancing (MLB) scheme is proposed to solve persistent congestion problems in next-generation wireless networks, in particular, due to an uneven spatial traffic distribution, which typically leads to an inefficient usage of resources. A key feature of the proposed algorithm is that not only the parameters are optimized, but also the parameter tuning strategy. Secondly, a novel MLB algorithm for enterprise femtocells scenarios is proposed. Such scenarios are characterized by the lack of a thorough deployment of these low-cost nodes, meaning that a more efficient use of radio resources can be achieved by applying effective MLB schemes. As in the previous problem, the optimization of the self-tuning process is also studied in this case. Thirdly, a new self-tuning algorithm for Mobility Robustness Optimization (MRO) is proposed. This study includes the impact of context factors such as the system load and user speed, as well as a proposal for coordination between the designed MLB and MRO functions. Fourthly, a novel self-tuning algorithm for Traffic Steering (TS) in heterogeneous networks is proposed. The main features of the proposed algorithm are the flexibility to support different operator policies and the adaptation capability to network variations. Finally, with the aim of validating the proposed techniques, a dynamic system-level simulator for Long-Term Evolution (LTE) networks has been designed

Physical Layer Techniques for High Frequency Wireline Broadband Systems

This thesis collects contributions to wireline and wireless communication systems with an emphasis on multiuser and multicarrier physical layer technology. To deliver increased capacity, modern wireline access systems such as G.fast extend the signal bandwidth up from tens to hundreds of MHz. This ambitious development revealed a number of unforeseen hurdles such as the impact of impedance changes in various forms. Impedance changes have a strong effect on the performance of multi-user crosstalk mitigation techniques such as vectoring. The first part of the thesis presents papers covering the identification of one of these problems, a model describing why it occurs and a method to mitigate its effects, improving line stability for G.fast systems.A second part of the thesis deals with the effects of temperature changes on wireline channels. When a vectored (MIMO) wireline system is initialized, channel estimates need to be obtained. This thesis presents contributions on the feasibility of re-using channel coefficients to speed up the vectoring startup procedures, even after the correct coefficients have changed, e.g., due to temperature changes. We also present extensive measurement results showing the effects of temperature changes on copper channels using a temperature chamber and British cables. The last part of the thesis presents three papers on the convergence of physical layer technologies, more specifically the deployment of OFDM-based radio systems using twisted pairs in different ways. In one proposed scenario, the idea of using the access copper lines to deploy small cells inside users' homes is explored. The feasibility of the concept, the design of radio-heads and a practical scheme for crosstalk mitigation are presented in three contributions

Building the Future Internet through FIRE

The Internet as we know it today is the result of a continuous activity for improving network communications, end user services, computational processes and also information technology infrastructures. The Internet has become a critical infrastructure for the human-being by offering complex networking services and end-user applications that all together have transformed all aspects, mainly economical, of our lives. Recently, with the advent of new paradigms and the progress in wireless technology, sensor networks and information systems and also the inexorable shift towards everything connected paradigm, first as known as the Internet of Things and lately envisioning into the Internet of Everything, a data-driven society has been created. In a data-driven society, productivity, knowledge, and experience are dependent on increasingly open, dynamic, interdependent and complex Internet services. The challenge for the Internet of the Future design is to build robust enabling technologies, implement and deploy adaptive systems, to create business opportunities considering increasing uncertainties and emergent systemic behaviors where humans and machines seamlessly cooperate

Building the Future Internet through FIRE

The Internet as we know it today is the result of a continuous activity for improving network communications, end user services, computational processes and also information technology infrastructures. The Internet has become a critical infrastructure for the human-being by offering complex networking services and end-user applications that all together have transformed all aspects, mainly economical, of our lives. Recently, with the advent of new paradigms and the progress in wireless technology, sensor networks and information systems and also the inexorable shift towards everything connected paradigm, first as known as the Internet of Things and lately envisioning into the Internet of Everything, a data-driven society has been created. In a data-driven society, productivity, knowledge, and experience are dependent on increasingly open, dynamic, interdependent and complex Internet services. The challenge for the Internet of the Future design is to build robust enabling technologies, implement and deploy adaptive systems, to create business opportunities considering increasing uncertainties and emergent systemic behaviors where humans and machines seamlessly cooperate