Enabling self organisation for future cellular networks.

The rapid growth in mobile communications due to the exponential demand for wireless access is causing the distribution and maintenance of cellular networks to become more complex, expensive and time consuming. Lately, extensive research and standardisation work has been focused on the novel paradigm of self-organising network (SON). SON is an automated technology that allows the planning, deployment, operation, optimisation and healing of the network to become faster and easier by reducing the human involvement in network operational tasks, while optimising the network coverage, capacity and quality of service. However, these SON autonomous features cannot be achieved with the current drive test coverage assessment approach due to its lack of automaticity which results in huge delays and cost. Minimization of drive test (MDT) has recently been standardized by 3GPP as a key self- organising network (SON) feature. MDT allows coverage to be estimated at the base station using user equipment (UE) measurement reports with the objective to eliminate the need for drive tests. However, most MDT based coverage estimation methods recently proposed in literature assume that UE position is known at the base station with 100% accuracy, an assumption that does not hold in reality. In this work, we develop a novel and accurate analytical model that allows the quantification of error in MDT based autonomous coverage estimation (ACE) as a function of error in UE as well as base station (user deployed cell) positioning. We first consider a circular cell with an omnidirectional antenna and then we use a three-sectored cell and see how the system is going to be affected by the UE and the base station (user deployed cell) geographical location information errors. Our model also allows characterization of error in ACE as function of standard deviation of shadowing in addition to the path-loss

Mobilfunknetzmanagement im Kontext von Realistischen Heterogenen Szenarien

Every generation of mobile radio communication standards leads to a new level of complexity in the cellular systems. Moreover, due to the ever-increasing data traffic demands of mobile users as well as declining revenues in recent years, the operators of such networks have to deal with all those network administration difficulties in the most efficient manner. One promising approach that shall relieve the operator from time-consuming manual tasks is to use so-called Self-Organising Network (SON) functionalities. SON functions monitor the performance of the network and change the (radio) parameters accordingly, based on internal algorithms that focus on dedicated optimisation goals. This work investigates whether SON functions can be used to enforce Key Performance Indicator (KPI) targets demanded by the operators. Therefore, the impact of SON on the network manageability and performance is studied by using SON functions that consider multiple technologies (i.e. LTE and WLAN) and different cell layers (macro and small cells). The evaluations are based on sophisticated system-level simulations that rely on an in-house developed platform called ``SiMoNe'' (Simulator for Mobile Networks). Moreover, the foundations of the scenarios used are realistically planned mobile networks on the one hand, and advanced mobility models with a particular emphasis on realistic movements and behaviours, on the other hand. As a preparatory step, the newly introduced mobility models are investigated regarding the handover performance. The results show that the behaviour and nature of the movements have a profound impact on the overall network performance. After that, three well-known SON functions are tested that operate in the domain of self-optimisation. This is done by varying SON algorithm parameterisation values in three distinct network environments. The insights gained into the behaviour of the SON functions are then used to manage a complex heterogeneous cellular network by setting appropriate SON parametrisation values that alter the behaviour of SON functions accordingly. By that, the formulated KPI goals can be achieved. However, the evaluations show that the implementations of the objectives are only doable to some extent in realistic settings due to the compound and inhomogeneous nature of the network scenarios.Jede neue Mobilfunk-Generation sorgt dafür, dass die Komplexität in den Netzen zunimmt. Außerdem führt die immer weiter steigende Nachfrage nach mobilem Datenverkehr sowie sinkende Einnahmen dazu, dass die Betreiber solcher Netze mit administrativen Aufgaben in möglichst effizienter Weise umgehen müssen. Eine Möglichkeit stellen sogenannte Selbst-Organisierende Netze (engl. Self-Organising Network (SON)) dar, um den Betreiber von zeitaufwendigen manuellen Arbeiten zu befreien. SON Funktionen überwachen Kenngrößen im Netz und ändern, je nach Zielfunktion des Algorithmus, entsprechende (Radio-)Parameter im Netz. Diese Dissertation untersucht, ob SON Funktionen geeignet sind um ein Mobilfunknetz zu steuern und somit vorgegebene Zielvorgaben der Netzbetreiber umzusetzen. Die verwendeten SON Funktionen arbeiten hierbei mit unterschiedlichen Technologien (z.B. LTE und WLAN) und auf mehreren Zellschichten (Makro- bis Femtozellen). Als Simulationsumgebung wird auf die leistungsfähige Plattform ``SiMoNe'' (engl. Simulator for Mobile Networks) zurückgegriffen. Die Simulationsgrundlagen bilden einerseits realistisch geplante Mobilfunknetze und anderseits fortschrittliche Mobilitätsmodelle, wobei eine besondere Betonung auf die realistische Umsetzung von Bewegung und Verhalten der Nutzer gelegt wird. In einem vorbereitenden Schritt werden neuartige Mobilitätsmodelle auf ihr Handover-Verhalten untersucht. Die Ergebnisse zeigen hierbei, dass das Verhalten und die Bewegung einen entscheidenden Einfluss auf die Netzperformance haben können. Im Anschluss werden drei bekannte SON Funktionen in drei unterschiedlichen Netzumgebungen getestet. Dies geschieht durch eine Variation der Parameterwerte der SON Algorithmen, welche das Verhalten der Funktionen verändern und somit auch die Netzperformances entscheidend beeinflussen kann. Die über das Verhalten der SON Funktionen gesammelten Erkenntnisse werden letztendlich genutzt, um Zielvorgaben an ein komplexes heterogenes Mobilfunknetzwerk zu realisieren. Die Auswertungen zeigen, dass dies nur in einem gewissen Maße geschehen kann. Die hohe Komplexität und die inhomogene Topologie der Netze beeinträchtigen eine zielgenaue Veränderung der Netzperformance entscheidend

Contribución al estudio de técnicas Self Organizing & Self Optimizing Networks para redes de comunicaciones móviles LTE

La aparición continua de nuevos servicios que consumen grandes anchos de banda, unida a la creciente demanda de acceso a Internet por parte de los usuarios en cualquier lugar en el que se encuentren, está aumentando considerablemente la complejidad de las redes de telefonía móvil. Los mecanismos actuales permiten gestionar los limitados recursos radioeléctricos en redes heterogéneas GSM/UMTS/LTE. Mediante el establecimiento de una estructura jerárquica celular, y unas funcionalidades de gestión multicapa, se puede distribuir el tráfico de voz y datos para ofrecer el mejor servicio a los clientes. Por otro lado, la movilidad de los usuarios y su distribución geográfica es muy variable dentro de un mismo territorio, por lo que las redes deben también adaptarse a este escenario. En los entornos urbanos se requiere un diseño de red con muchos elementos, en el que coexistirán células de diferentes tipos (macro, micro, pico, etc.) según la demanda de servicio, concentración de clientes y su movilidad.Además, estas redes han ido evolucionando tecnológicamente, encontrándonos en este momento en España con sistemas GSM 900, DCS 1800, UMTS 2100, UMTS 900 y LTE 1800 (a corto plazo LTE 800), que están en servicio simultáneamente, con un alto grado de relación y traspasos entre ellos. Para ofrecer continuidad del servicio entre todas las redes, y con el objeto de obtener la máxima rentabilidad aprovechando las inversiones realizadas en la infraestructura actual (GSM, UMTS R99, HSPA), la definición de la norma LTE contempla el mecanismo de ¿interworking¿, que consiste en un conjunto de funciones para permitir la interacción entre todas la redes que ofrecen el servicio de telefonía móvil. Este aumento de la complejidad requerirá nuevas inversiones con el objeto de gestionar de forma adecuada las labores de optimización, operación y mantenimiento de las redes, y en consecuencia, poder adaptarse a un mercado tan cambiante en el que constantemente están apareciendo nuevos servicios, terminales y modelos de negocio. En este sentido, aparece el concepto SON, que significa Self Organizing Networks, y tiene como objetivo la automatización de arduas tareas en la configuración, puesta en servicio, y optimización de parámetros de red, así como la de responder adecuadamente a eventualidades, consiguiendo con todo ello una reducción en los costes de operación y una mejora sustancial de la calidad de la red. La movilidad de los usuarios es una de las principales características del servicio de telefonía móvil, por lo que uno de los métodos para garantizar la Calidad consiste en un correcto diseño de relación de colindancias entre células cercanas, de tal manera que el terminal pueda disponer siempre de una célula a la que asociarse mientras se desplaza, dando así continuidad al servicio. En este trabajo de tesis se pretende diseñar un algoritmo de optimización automática que genere una relación de colindancias entre células para ofrecer la mejor calidad posible de la red.In this work we present theoretical studies on the characteristics of the cellular structures employed in the mobile communications networks, where there is a special emphasis on the interference and over reach like main limiting element of coverage, capacity and data rate. It also details the current trends of the different methods of optimization and shown a series of case studies carried out in the UMTS network of Telefónica, the results can be extrapolated to the LTE system. As a solution to the constraints of a real network compared to the theoretical designs, it is proposed in this thesis an ANR algorithm (Automatic Neighbour Relation) for the generation of neighbour lists which optimize the transfer between cells, achieving an increase in the number of completed calls and reduce the dropped calls or interrupted in the link radio Propagation models show the differences in free space loss with respect to complex urban environments, as well as the effects that produces the mobility of terminals in the characterization of the mobile channel. This feature is especially relevant in the heterogeneous scenarios with users where the communication is done through almost free spread, against others where the signal reaches them very attenuated and distorted after multiple reflections. The search for an optimal solution that offers good coverage, quality and capacity at the lowest cost, it is in this case a very complex task, so it is necessary to study the different lines of research in this area. In addition, the arrival of the LTE brings with it a cheaper and simplification of network structure, which includes the automation of the tasks of optimization. Consensus in different international forums and projector, described in this thesis the use cases and the most common algorithms and methods from several authors. To evaluate the characteristics of the test scenarios, measurements analysis and simulations were realized using innovative methods in order to obtain a characterization of the system in situations of high interference. In a first phase were implemented changes to the configuration of isolated cells, with the purpose of checking the mutual dependence that exists between all cells. With this procedure it was demonstrated that in dense scenarios, it is not possible to optimize the performance of a cell or base station without produce effects on the environment cells. With the conclusions of the previous tests there was designed a novel ANR algorithm that proposes different neighbor lists according to a set of constrains. Power measurements and interference obtained by a call traced tool, showed values very scattered and sometimes opposite. This makes difficult the selection of the best adjacent cell to complete a handover when the subscribers move. The algorithm is capable of combining the best option for a very wide area of the network with high interference, which represents a considerable improvement over the usual methods of neighbor list definition. Designed algorithm applied in the UMTS network of Telefónica, which is located in the Valle de la Orotava, and includes the towns of Puerto de la Cruz, La Orotava and Los Realejos. By the topography of the valley and the dispersion of the population, levels of interference and overreach are greater than in a normal urban scenario, so the net performance are lower. With the proposed method was obtained an increase in the total number of successfully calls, and reduced the number of dropped or interrupted calls