Measurement and Optimization of LTE Performance

4G Long Term Evolution (LTE) mobile system is the fourth generation communication system adopted worldwide to provide high-speed data connections and high-quality voice calls. Given the recent deployment by mobile service providers, unlike GSM and UMTS, LTE can be still considered to be in its early stages and therefore many topics still raise great interest among the international scientific research community: network performance assessment, network optimization, selective scheduling, interference management and coexistence with other communication systems in the unlicensed band, methods to evaluate human exposure to electromagnetic radiation are, as a matter of fact, still open issues. In this work techniques adopted to increase LTE radio performances are investigated. One of the most wide-spread solutions proposed by the standard is to implement MIMO techniques and within a few years, to overcome the scarcity of spectrum, LTE network operators will offload data traffic by accessing the unlicensed 5 GHz frequency. Our Research deals with an evaluation of 3GPP standard in a real test best scenario to evaluate network behavior and performance

Models of Control Channels in the LTE System

Dizertační práce se zabývá zpracováním signálu fyzických řídicích kanálů systému LTE a vyšetřováním bitové chybovosti při přenosu řídicí informace z vysílače do přijímače v závislosti na podmínkách příjmu. Práce je rozdělena do dvou hlavních částí. První část práce je zaměřena na simulaci přenosu řídicí informace LTE v základním pásmu. Jsou zde prezentovány vytvořené simulátory řídicích kanálů ve směru uplink i downlink. Simulace jsou provedeny pro všechny druhy nastavení systému a základní modely přenosového prostředí. Jsou zde popsány výsledky vlivu použití MIMO technologií na kvalitu příjmu řídicí informace především v únikových kanálech. Druhá část práce je zaměřena na možnost nasazení systému LTE ve sdíleném pásmu ISM (2.4 GHz). Jsou zde představeny základní koncepce použití, na jejichž základě je vytvořen scénář simulací. Kapitola dále popisuje tvorbu simulátoru koexistence LTE a systému Wi-Fi v přeneseném pásmu ISM 2.4GHz. Jsou zde uvedeny výsledky simulací koexistence LTE a rušivého systému Wi-Fi provedených dle vytvořeného scénáře. Výsledky simulací koexistence LTE a Wi-Fi jsou ověřeny měřením v laboratorních podmínkách. Toto porovnání je důležité z hlediska optimalizace simulátoru koexistence. Dle výsledků obou typů simulací a měření jsou stanovena provozní doporučení, která mají přispět k bezpečnému a spolehlivému vysílání a příjmu řídicích informací LTE i při nepříznivých podmínkách příjmu.The doctoral thesis is focused on a signal processing in the LTE physical control channels and performance analysis of control information transmission according to receiving conditions. The thesis is divided into two parts. The first part deals with simulation of the transmission of control information in baseband. The created simulators for uplink and downlink are presented. The simulations are performed for all possible system settings and various channel models. The MIMO influence on a quality of control information reception under fading channels is also presented. The second part of the thesis is focused on LTE utilization in shared channel ISM (2.4 GHz). The basic LTE application concept for ISM band is presented. This concept is fundamental to created simulation scenario. The chapter also presents the LTE and Wi-Fi coexistence simulator in 2.4 GHz ISM passband. The coexistence simulation are presented according to simulation scenario and the results are shown. The simulated coexistence analysis results are verified in laboratory environment. The comparison of the simulated and the measured coexistence analysis results is crucial for further optimization of the coexistence simulator. Recommendations for optimal and reliable operation of LTE are specified according to the simulated and the measured results. Recommendations should be useful to the reliable transmission of LTE control information in bad receiving conditions.

Radio frequency interference to DVB-T reception from LTE systems in adjacent bands

Australians have recently benefited from the switch-over to digital television which has freed many channels called digital dividend. Australia's digital dividend is the frequency range of 694 MHz to 820 MHz which is used to operate Long Term Evolu- tion (LTE) technology. In Australia there were 57 VHF and UHF channels used for television broadcasting. After the completion of switch-over process, UHF channels 52 to 69 were freed up which is considered as Australian digital dividend. When LTE Frequency Division Duplex (FDD) system and digital television services operate in adjacent UHF bands, LTE FDD transmitters can cause harmful interference to digital video broadcasting-terrestrial (DVB-T). So in this study, we have presented the compatibility of operating LTE FDD services in the digital dividend spectrum identified in Australia. We have used interference analysis method to calculate the minimum separation distance between LTE FDD and DVB-T sys- tem and Monte Carlo Simulation for calculating the probability of location within considered DVB-T area that suffer maximum level of interference. Also, there are some unused channels where digital television operates called TV White Spaces (TVWS). TVWS can be utilized to operate the secondary devices such as LTE Time Division Duplex (TDD) which helps to address spectrum scarcity issue. We have presented the study of the interference on DVB-T when LTE TDD are operating on TVWS. We have used interference analysis method to calculate mini- mum separation distance between LTE TDD and DVB-T. The results of our study show that increasing the guard band reduces the interference to adjacent channel

Enabling Disaster Resilient 4G Mobile Communication Networks

The 4G Long Term Evolution (LTE) is the cellular technology expected to outperform the previous generations and to some extent revolutionize the experience of the users by taking advantage of the most advanced radio access techniques (i.e. OFDMA, SC-FDMA, MIMO). However, the strong dependencies between user equipments (UEs), base stations (eNBs) and the Evolved Packet Core (EPC) limit the flexibility, manageability and resiliency in such networks. In case the communication links between UEs-eNB or eNB-EPC are disrupted, UEs are in fact unable to communicate. In this article, we reshape the 4G mobile network to move towards more virtual and distributed architectures for improving disaster resilience, drastically reducing the dependency between UEs, eNBs and EPC. The contribution of this work is twofold. We firstly present the Flexible Management Entity (FME), a distributed entity which leverages on virtualized EPC functionalities in 4G cellular systems. Second, we introduce a simple and novel device-todevice (D2D) communication scheme allowing the UEs in physical proximity to communicate directly without resorting to the coordination with an eNB.Comment: Submitted to IEEE Communications Magazin

Learning-based mechanism to enhance LTE-U operation

Nowadays, mobile communications are evolving to more complex systems and environments, LTE-U is a clear example as it needs to work in the unlicensed spectrum, which is a highly occupied and changing environment. A good solution for the channel selection in this case is using learning mechanisms. Learning techniques provide the systems with the ability to learn from the environment in order to make the best decisions. In this thesis you can find the evolution of the LTE technology until arriving to LTE-U, and also a brief explanation about learning. The project also explores evolutions of a given channel selection algorithm based in Q-learning, firstly finding initial values that make it work better and, secondly, proposing some variations in order to improve its performance.Hoy en día, las comunicaciones móviles están evolucionando hacia sistemas y entornos más complejos, LTE-U es un claro ejemplo ya que tiene que operar en el espectro libre, que es un entorno altamente ocupado y en constante cambio. Una buena solución para la selección de canal en este caso es el uso de mecanismos de aprendizaje. Las técnicas de aprendizaje proveen a los sistemas la habilidad de aprender de su entorno para poder tomar las mejores decisiones posibles. En esta tesis podréis encontrar la evolución de la tecnología LTE hasta llegar a LTE-U, y también una breve explicación sobre el aprendizaje. El proyecto también explora evoluciones de un algoritmo de selección de canal basado en Q-learning librado previamente, primero encontrando valores iniciales que lo hacen trabajar mejor y, después, proponiendo algunas variaciones para aumentar su rendimiento.Avui en dia, les comunicacions mòbils estan evolucionant cap a sistemes i entorns més complexos, l’LTE-U n’és un clar exemple ja que ha d’operar en l’espectre lliure, que és un entorn molt ocupat i constantment en canvi. Una bona solució per la selecció de canal és, en aquest cas, fer servir mecanismes d’aprenentatge. Les tècniques d’aprenentatge donen als sistemes l’habilitat d’aprendre de l’entorn per poder prendre les millors decisions possibles. En aquesta tesi podreu trobar l’evolució de la tecnologia LTE fins arribar a l’LTE-U, i també una breu explicació sobre l’aprenentatge. El projecte també explora evolucions d’un algorisme de selecció de canal basat en Q-learning lliurat prèviament, primer trobant valors inicials que el fan treballar millor i, després, proposant algunes variacions per augmentar el seu rendiment

Characterization of Channel Selection in LTE-U based on Q-Learning

To assess the performance of a Q-learning technique for channel selection in LTE-U under different conditions of parameter settings and scenarios, and to optimize the performance of the technique by modifying their parameters and/or operation procedure.The usage of LTE in unlicensed bands is a topic of great interest among the telecommunications companies and organizations, given the many advantages it can bring. For this reason, many feasibility studies have been conducted in order to define a standard for this technology. One of the approaches proposed is to apply the Q-Learning algorithm to the Channel Selection in LTE-U. Many promising results have already been achieved, so this technique deserves further insights. The objective of this Thesis is to assess the performance of this algorithm under different conditions of parameter settings and scenarios in order to optimize the performance of the technique by modifying the parameters and the operation procedure. The items analysed are the impact of the Initial Temperature, of the Learning Rate, of the positions of the SCs and of the number of active users