Uplink Resource Allocation in Relay Enhanced LTE-Advanced Cellular Networks

In parallel to HSPA evolution, 3GPP has adopted the Long Term Evolution track to fulfill the performance targets of 4G cellular networks. Multi-hop networks consisting of fixed decode and forward relays nodes are proposed to relax the capacity and coverage limitations encountered by traditional macro base station deployments. The relays are designed to operate on the in-band spectrum and support self-backhauling of user data. This thesis work provides an insight into the impact of uplink resource allocation in delivering improved user experience in relay enhanced cellular networks. Radio resource allocation and power control play a crucial role in the performance of wireless communication systems. System level simulations reveal that reuse 1 based relay enhanced cells operate in an interference limited scenario. Therefore, a resource allocation scheme based on user grouping is investigated to coordinate and mitigate the negative effect of interference. It is shown that the proposed methodology is spectrally efficient and delivers improved system performance. In addition to improving system performance, relaying is seen to be beneficial in significantly reducing battery consumption in devices. This is highly appealing since the next generation cellular networks are targeted towards higher bit rates and extended periods of mobile data usage. This work provides specific insights into the performance limiting criteria of the envisaged multi-hop system and, furthermore, is expected to contribute towards 3GPP's standardization of the relaying study item

Pré-codificação e equalização para sistemas SC-FDMA heterogéneos

Mestrado em Engenharia Electrónica e TelecomunicaçõesMobile traffic in cellular networks is increasing exponentially. Small-cells are considered as a key solution to meet these requirements. Under the same spectrum the small-cells and the associated macro-cell (forming the so called heterogeneous systems) must cooperate so that one system can adapt to the other. If no cooperation is considered then the small-cells will generate harmful interference at the macro-cell. Interference alignment (IA) is a precoding technique that is able to achieve the maximum degrees of freedom of the interference channel, and can efficiently deal with inter-systems interference. Single carrier frequency division multiple access (SC-FDMA) is a promising solution technique for high data rate uplink communications in future cellular systems. Conventional linear equalizers are not efficient to remove the residual inter-carrier interference of the SC-FDMA systems. For this reason, there has been significant interest in the design of nonlinear frequency domain equalizers in general and decision feedback equalizers in particular, with the iterative block decision feedback equalizer (IB-DFE) being the most promising nonlinear equalizer. In this dissertation we propose and evaluate joint interference alignment precoding at the small cell user terminals with iterative non-linear frequency domain equalizer at the receivers (macro base station and central unit) for SC-FDMA based heterogeneous networks. The small-cell precoders are designed by enforcing that all generated interference at the macro-cell is aligned in an orthogonal subspace to the macro-cell received signal subspace. This enforces that no performance degradation is observed at the macro cell. Then, we design an iterative nonlinear frequency domain equalizer at the macro-cell receiver that is able to recover the macro-cell spatial streams, in the presence of both small-cell and inter-carrier interferences. The results show that the proposed transmitter and receiver structures are robust to the inter-system interferences and at the same time are able to efficient separate the macro and small cells spatial streams.O trafego móvel nas redes celulares tem aumentado exponencialmente. As pico- células são consideradas como a solução chave para cumprir estes requisitos. Dentro do mesmo espectro, as pico-células e as macro-células (formando os chamados sistemas heterogéneos) precisam de colaborar de modo a que um sistema possa adaptar-se ao outro. Se não for considerada a cooperação, então as pico-células irão gerar interferência prejudicial na macro-célula. Interference alignment (IA) é uma técnica de précodificação que é capaz de atingir o grau máximo de liberdade do canal de interferência, e consegue lidar eficazmente com interferência entre sistemas. Single carrier frequency division multiple access (SC-FDMA) é uma solução técnica promissora para transmissão de dados em uplink, para sistemas celulares futuros. Equalizadores lineares convencionais não são eficientes a remover a interferência residual entre portadoras dos sistemas SC-FDMA. Por este motivo, tem havido interesse significativo no desenho de equalizadores não lineares no domínio da frequência em geral e em equalizadores baseados em decisão por feedback em particular, tendo o iterative block decision feedback equalizer (IB-DFE) como o equalizador não linear mais promissor. Nesta dissertação propomos e avaliamos précodificação de alinhamento de interferência nos terminais das pico-células em conjunto com equalizadores não lineares no domínio da frequência nos recetores (estação base da macro-célula e unidade central de processamento) para redes heterogéneas baseadas em SC-FDMA. Os précodificadores das pico-células são desenhados de maneira a obrigar a que toda a interferência gerada na macro-célula esteja alinhada num subespaço ortogonal em relação ao subespaço do sinal recebido na macro- célula. Isto obriga a que não seja observada degradação de desempenho na macro-célula. Em seguida, desenhamos um equalizador não linear no domínio da frequência no recetor da macro-célula capaz de recuperar os fluxos de dados da macro-célula, na presença de interferência tanto entre portadoras como das pico-células. Os resultados mostram que as estruturas de transmissão e receção propostas são robustas contra a interferência entre sistemas e ao mesmo tempo capaz de separar eficientemente os dados da macro e das pico células

Final report on the evaluation of RRM/CRRM algorithms

Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin

On the Performance Gain of NOMA over OMA in Uplink Communication Systems

In this paper, we investigate and reveal the ergodic sum-rate gain (ESG) of non-orthogonal multiple access (NOMA) over orthogonal multiple access (OMA) in uplink cellular communication systems. A base station equipped with a single-antenna, with multiple antennas, and with massive antenna arrays is considered both in single-cell and multi-cell deployments. In particular, in single-antenna systems, we identify two types of gains brought about by NOMA: 1) a large-scale near-far gain arising from the distance discrepancy between the base station and users; 2) a small-scale fading gain originating from the multipath channel fading. Furthermore, we reveal that the large-scale near-far gain increases with the normalized cell size, while the small-scale fading gain is a constant, given by $\gamma$ = 0.57721 nat/s/Hz, in Rayleigh fading channels. When extending single-antenna NOMA to $M$-antenna NOMA, we prove that both the large-scale near-far gain and small-scale fading gain achieved by single-antenna NOMA can be increased by a factor of $M$ for a large number of users. Moreover, given a massive antenna array at the base station and considering a fixed ratio between the number of antennas, $M$, and the number of users, $K$, the ESG of NOMA over OMA increases linearly with both $M$ and $K$. We then further extend the analysis to a multi-cell scenario. Compared to the single-cell case, the ESG in multi-cell systems degrades as NOMA faces more severe inter-cell interference due to the non-orthogonal transmissions. Besides, we unveil that a large cell size is always beneficial to the ergodic sum-rate performance of NOMA in both single-cell and multi-cell systems. Numerical results verify the accuracy of the analytical results derived and confirm the insights revealed about the ESG of NOMA over OMA in different scenarios.Comment: 51 pages, 7 figures, invited paper, submitted to IEEE Transactions on Communication

Efficient Scheduling Algorithms for Wireless Resource Allocation and Virtualization in Wireless Networks

The continuing growth in demand for better mobile broadband experiences has motivated rapid development of radio-access technologies to support high data rates and improve quality of service (QoS) and quality of experience (QoE) for mobile users. However, the modern radio-access technologies pose new challenges to mobile network operators (MNO) and wireless device designers such as reducing the total cost of ownership while supporting high data throughput per user, and extending battery life-per-charge of the mobile devices. In this thesis, a variety of optimization techniques aimed at providing innovative solutions for such challenges are explored. The thesis is divided into two parts. In the first part, the challenge of extending battery life-per-charge is addressed. Optimal and suboptimal power-efficient schedulers that minimize the total transmit power and meet the QoS requirements of the users are presented. The second outlines the benefits and challenges of deploying wireless resource virtualization (WRV) concept as a promising solution for satisfying the growing demand for mobile data and reducing capital and operational costs. First, a WRV framework is proposed for single cell zone that is able to centralize and share the spectrum resources between multiple MNOs. Consequently, several WRV frameworks are proposed, which virtualize the spectrum resource of the entire network for cloud radio access network (C-RAN)- one of the front runners for the next generation network architecture. The main contributions of this thesis are in designing optimal and suboptimal solutions for the aforementioned challenges. In most cases, the optimal solutions suffer from high complexity, and therefore low-complexity suboptimal solutions are provided for practical systems. The optimal solutions are used as benchmarks for evaluating the suboptimal solutions. The results prove that the proposed solutions effectively contribute in addressing the challenges caused by the demand for high data rates and power transmission in mobile networks

Implementação de um sistema de comunicações móveis para o Uplink

Mestrado em Engenharia Electrónica e TelecomunicaçõesÉ evidente que actualmente cada vez mais a internet móvel está presente na vida das sociedades. Hoje em dia é relativamente fácil estar ligado à internet sempre que se quiser, independentemente do lugar onde se encontra (conceito: anytime and anywhere). Desta forma existe um número crescente de utilizadores que acedem a serviços e aplicações interactivas a partir dos seus terminais móveis. Há, portanto, uma necessidade de adaptar o mundo das telecomunicações a esta nova realidade, para isso é necessário implementar novas arquitecturas que sejam capazes de fornecer maior largura de banda e reduzir os atrasos das comunicações, maximizando a utilização dos recursos disponíveis do meio/rede e melhorando assim a experiência do utilizador final. O LTE representa uma das tecnologias mais avançadas e de maior relevância para o acesso sem fios em banda larga de redes celulares. OFDM é a tecnologia base que está por traz da técnica de modulação, bem como as tecnologias adjacentes, OFDMA e SC-FDMA, usadas especificamente no LTE para a comunicação de dados descendente (downlink) ou ascendente (uplink), respectivamente. A implementação de múltiplas antenas em ambos os terminais, potenciam ainda mais o aumento da eficiência espectral do meio rádio permitindo atingir grandes taxas de transmissão de dados. Nesta dissertação é feito o estudo, implementação e avaliação do desempenho da camada física (camada 1 do modelo OSI) do LTE, no entanto o foco será a comunicação de dados ascendente e a respectiva técnica de modelação, SC-FDMA. Foi implementada uma plataforma de simulação baseada nas especificações do LTE UL onde foram considerandos diferentes esquemas de antenas. Particularmente para o esquema MIMO, usou-se a técnica de codificação no espaço-frequência proposta por Alamouti. Foram também implementados vários equalizadores. Os resultados provenientes da simulação demonstram tanto a eficiência dos diversos modos de operação em termos da taxa de erro, como o excelente funcionamento de processos de mapeamento e equalização, que visam melhorar a taxa de recepção de dados.It is clear that mobile Internet is present in the life of societies. Nowadays it is relatively easy to be connected to the internet whenever you want, no matter where you are (concept: anytime and anywhere). Thus, there are a growing number of users accessing interactive services and applications from their handsets. Therefore, there is a need to adapt the world of telecommunications to this new reality, for that it is necessary to implement new architectures that are able to provide higher bandwidth and reduce communication delays, maximizing use of available resources in the medium/network and thereby improving end-user experience. LTE represents one of the most advanced architectures and most relevant to wireless broadband cellular networks. OFDM is the technology that is behind the modulation technique and the underlying technologies, OFDMA and SCFDMA, used specifically in LTE for data communication downward (downlink) or upward (uplink), respectively. The implementation of multiple antennas at both ends further potentiate the increase of spectral efficiency allowing to achieve high rates of data transmission. In this dissertation is done the study, implementation and performance evaluation of the physical layer (OSI Layer 1) of the LTE, but the focus will be communication and its upstream data modeling technique, SC-FDMA. We implemented a simulation platform based on LTE UL specifications where were considered different antenna schemes. Particularly for the MIMO scheme, we used the technique of space-frequency coding proposed by Alamouti. We also implemented several equalizers. The results from the simulation demonstrate both the efficiency of different modes of operation in terms of error rate, as the excellent operation of mapping processes and equalization, designed to improve the rate of receiving data

4G/5G cellular networks metrology and management

La prolifération d'applications et de services sophistiqués s'accompagne de diverses exigences de performances, ainsi que d'une croissance exponentielle du trafic pour le lien montant (uplink) et descendant (downlink). Les réseaux cellulaires tels que 4G et 5G évoluent pour prendre en charge cette quantité diversifiée et énorme de données. Le travail de cette thèse vise le renforcement de techniques avancées de gestion et supervision des réseaux cellulaires prenant l'explosion du trafic et sa diversité comme deux des principaux défis dans ces réseaux. La première contribution aborde l'intégration de l'intelligence dans les réseaux cellulaires via l'estimation du débit instantané sur le lien montant pour de petites granularités temporelles. Un banc d'essai 4G temps réel est déployé dans ce but de fournir un benchmark exhaustif des métriques de l'eNB. Des estimations précises sont ainsi obtenues. La deuxième contribution renforce le découpage 5G en temps réel au niveau des ressources radio dans un système multicellulaire. Pour cela, deux modèles d'optimisation ont été proposés. Du fait de leurs temps d'exécution trop long, des heuristiques ont été développées et évaluées en comparaisons des modèles optimaux. Les résultats sont prometteurs, les deux heuristiques renforçant fortement le découpage du RAN en temps réel.The proliferation of sophisticated applications and services comes with diverse performance requirements as well as an exponential traffic growth for both upload and download. The cellular networks such as 4G and 5G are advocated to support this diverse and huge amount of data. This thesis work targets the enforcement of advanced cellular network supervision and management techniques taking the traffic explosion and diversity as two main challenges in these networks. The first contribution tackles the intelligence integration in cellular networks through the estimation of users uplink instantaneous throughput at small time granularities. A real time 4G testbed is deployed for such aim with an exhaustive metrics benchmark. Accurate estimations are achieved.The second contribution enforces the real time 5G slicing from radio resources perspective in a multi-cell system. For that, two exact optimization models are proposed. Due to their high convergence time, heuristics are developed and evaluated with the optimal models. Results are promising, as two heuristics are highly enforcing the real time RAN slicing

A Review of MAC Scheduling Algorithms in LTE System

The recent wireless communication networks rely on the new technology named Long Term Evolution (LTE) to offer high data rate real-time (RT) traffic with better Quality of Service (QoS) for the increasing demand of customer requirement. LTE provide low latency for real-time services with high throughput, with the help of two-level packet retransmission. Hybrid Automatic Repeat Request (HARQ) retransmission at the Medium Access Control (MAC) layer of LTE networks achieves error-free data transmission. The performance of the LTE networks mainly depends on how effectively this HARQ adopted in the latest communication standard, Universal Mobile Telecommunication System (UMTS). The major challenge in LTE is to balance QoS and fairness among the users. Hence, it is very essential to design a down link scheduling scheme to get the expected service quality to the customers and to utilize the system resources efficiently. This paper provides a comprehensive literature review of LTE MAC layer and six types of QoS/Channel-aware downlink scheduling algorithms designed for this purpose. The contributions of this paper are to identify the gap of knowledge in the downlink scheduling procedure and to point out the future research direction. Based on the comparative study of algorithms taken for the review, this paper is concluded that the EXP Rule scheduler is most suited for LTE networks due to its characteristics of less Packet Loss Ratio (PLR), less Packet Delay (PD), high throughput, fairness and spectral efficiency