63 research outputs found
Delay aware optimal resource allocation in MU MIMO-OFDM using enhanced spider monkey optimization
In multiple users MIMO- OFDM system allocates the available resources to the optimal users is a difficult task. Hence the scheduling and resource allocation become the major problem in the wireless network mainly in case of multiple input and multiple output method that has to be made efficient. There is various method introduced to give an optimal solution to the problem yet it has many drawbacks. So we propose this paper to provide an efficient solution for resource allocation in terms of delay and also added some more features such as high throughout, energy efficient and fairness. To make optimal resource allocation we introduce optimization algorithm named spider monkey with an enhancement which provides the efficient solution. In this optimization process includes the scheduling and resource allocation, the SNR values, channel state information (CSI) from the base station. To make more efficient finally we perform enhanced spider - monkey algorithm hence the resource allocation is performed based on QoS requirements. Thus the simulation results in our paper show high efficiency when compared with other schedulers and techniques
Radio Communications
In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks
Enhancing the energy efficiency of radio base stations
This thesis is concerned with the energy efficiency of cellular networks. It
studies the dominant power consumer in future cellular networks, the Long Term
Evolution (LTE) radio Base Station (BS), and proposes mechanisms that enhance
the BS energy efficiency by reducing its power consumption under target rate
constraints. These mechanisms trade spare capacity for power saving.
First, the thesis describes how much power individual components of a BS
consume and what parameters affect this consumption based on third party
experimental data. These individual models are joined into a component power
model for an entire BS. The component model is an essential step in analysis but is
too complex for many applications. It is therefore abstracted into a much simpler
parameterized model to reduce its complexity. The parameterized model is further
simplified into an affine model which can be applied in power minimization.
Second, Power Control (PC) and Discontinuous Transmission (DTX) are identified as promising power-saving Radio Resource Management (RRM) mechanisms
and applied to multi-user downlink transmission. PC reduces the power consumption
of the Power Amplifier (PA) and is found to be most effective at high
traffic loads. DTX mostly reduces the power consumption of the Baseband (BB)
unit while interrupting transmission and is better applied in low traffic loads.
Joint optimization of these two techniques is found to enable additional power-saving
at medium traffic loads and to be a convex problem which can be solved
efficiently. The convex problem is extended to provide a comprehensive power-saving
Orthogonal Frequency Division Multiple Access (OFDMA) frame resource
scheduler. The proposed scheduler is shown to reduce power consumption by
25-40% in computer simulations, depending on the traffic load.
Finally, the thesis investigates the influence of interference on power consumption
in a network of multiple power-saving BSs. It discusses three popular alternative
distributed uncoordinated methods which align DTX mode between neighbouring
BSs. To address drawbacks of these three, a fourth memory-based DTX alignment
method is proposed. It decreases power consumption by up to 40% and
retransmission probability by around 20%, depending on the traffic load
Implementation of New Multiple Access Technique Encoder for 5G Wireless Telecomunication Networks
RÉSUMÉ Les exigences de la connectivité mobile massive de différents appareils et de diverses applications déterminent les besoins des prochaines générations de technologies mobiles (5G) afin de surmonter les demandes futures. L'expansion significative de la connectivité et de la densité du trafic caractérisent les besoins de la cinquième génération de réseaux mobiles. Par conséquent, pour la 5G, il est nécessaire d'avoir une densité de connectivité beaucoup plus élevée et une plus grande
portée de mobilité, un débit beaucoup plus élevé et une latence beaucoup plus faible. En raison de l'exigence d'une connectivité massive, de nombreuses nouvelles technologies
doivent être améliorées: le codage des canaux, la technique d'accès multiple, la modulation et la diversité, etc. Par conséquent, compte tenu de l'environnement 5G, surcoût de signalisation et de la latence devrait être pris en compte [1]. En outre, l'application de la virtualisation des accès sans fil (WAV) devrait également être considérée et, par conséquent, il est également nécessaire de concevoir la plate-forme matérielle prenant en charge les nouvelles normes pour la mise en œuvre des émetteurs-récepteurs virtuels. L'une des nouvelles technologies possibles pour la 5G est l'accès multiple pour améliorer
le débit. Par conséquent, au lieu d'OFDMA utilisé dans la norme LTE (4G), l'application d'une nouvelle technique d'accès multiple appelée Sparse Code Multiple Access (SCMA) est investiguée dans cette dissertation. SCMA est une nouvelle technique d'accès multiple non orthogonale du
domaine fréquentiel proposée pour améliorer l'efficacité spectrale de l'accès radio sans fil [2]. L'encodage SCMA est l'un des algorithmes les plus simples dans les techniques d'accès multiple qui offre l'opportunité d'expérimenter des méthodes génériques de mise en oeuvre. En outre, la nouvelle méthode d'accès multiple est supposée fournir un débit plus élevé. Le choix du codage
SCMA avec moins de complexité pourrait être une approche appropriée. La cible fixée pour cette recherche était d'atteindre un débit d’encodage de plus de 1 Gbps pour le codeur SCMA. Les implémentations de codage SCMA ont été effectuées à la fois en logiciel et en matériel
pour permettre de les comparer. Les implémentations logicielles ont été développées avec le langage de programmation C. Parmi plusieurs conceptions, la performance a été améliorée en utilisant différentes méthodes pour augmenter le parallélisme, diminuer la complexité de calcul et par conséquent le temps de traitement.----------ABSTRACT The demands of massive mobile connectivity of different devices and diverse applications
at the same time set requirments for next generations of mobile technology (5G). The significant expansion of connectivity and traffic density characterize the requirements of fifth generation mobile. Therefore, in 5G, there is a need to have much higher connectivity density, higher mobility ranges, much higher throughput, and much lower latency. In pursuance of the requirement of massive connectivity, numerous technologies must be
improved: channel coding, multiple access technique, modulation and diversity, etc. For instance,
with 5G, the cost of signaling overhead and latency should be taken into account [1]. Besides, applying wireless access virtualization (WAV) should be considered and there is also a need to have effective implementations supporting novel virtual transceiver. One of the possible new technologies for 5G is exploiting multiple access techniques to improve throughput. Therefore, instead of OFDMA in LTE (4G), applying a new multiple access
technique called Sparse Code Multiple Access (SCMA) is an approach considered in this dissertation. SCMA is a new frequency domain non-orthogonal multiple access technique proposed to improve spectral efficiency of wireless radio access [2]. SCMA encoding is one of the simplest
multiple access technique that offers an opportunity to experiment generic implementation methods. In addition, the new multiple access method is supposed to provide higher throughput, thus choosing SCMA encoding with less complexity could be an appropriate approach. The target
with SCMA was to achieve an encoding throughput of more that 1Gbps. SCMA encoding implementations were done both in software and hardware to allow comparing them. The software implementations were developed with the C programing language. Among several designs, the performance was improved by using different methods to increase
parallelism, decrease the computational complexity and consequently the processing time. The best achieved results with software implementations offer a 3.59 Gbps throughput, which is 3.5 times more that the target. For hardware implementation, high level synthesis was experimented. In order to do that, the C based functions and testbenches which were developed for software implementations, were
used as inputs to Vivado HLS
Review of Recent Trends
This work was partially supported by the European Regional Development Fund (FEDER), through the Regional Operational Programme of Centre (CENTRO 2020) of the Portugal 2020 framework, through projects SOCA (CENTRO-01-0145-FEDER-000010) and ORCIP (CENTRO-01-0145-FEDER-022141). Fernando P. Guiomar acknowledges a fellowship from “la Caixa” Foundation (ID100010434), code LCF/BQ/PR20/11770015. Houda Harkat acknowledges the financial support of the Programmatic Financing of the CTS R&D Unit (UIDP/00066/2020).MIMO-OFDM is a key technology and a strong candidate for 5G telecommunication systems. In the literature, there is no convenient survey study that rounds up all the necessary points to be investigated concerning such systems. The current deeper review paper inspects and interprets the state of the art and addresses several research axes related to MIMO-OFDM systems. Two topics have received special attention: MIMO waveforms and MIMO-OFDM channel estimation. The existing MIMO hardware and software innovations, in addition to the MIMO-OFDM equalization techniques, are discussed concisely. In the literature, only a few authors have discussed the MIMO channel estimation and modeling problems for a variety of MIMO systems. However, to the best of our knowledge, there has been until now no review paper specifically discussing the recent works concerning channel estimation and the equalization process for MIMO-OFDM systems. Hence, the current work focuses on analyzing the recently used algorithms in the field, which could be a rich reference for researchers. Moreover, some research perspectives are identified.publishersversionpublishe
Recent Advances in Wireless Communications and Networks
This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters
Cooperative diversity schemes for wireless communication systems
Mestrado em Engenharia Electrónica e TelecomunicaçõesA presente dissertação insere-se na área das comunicações sem fios, ou mais especificamente na temática da diversidade cooperativa.
Neste trabalho é feito o estudo, implementação e avaliação do desempenho de esquemas de diversidade cooperativa de baixa complexidade para sistemas de comunicação móvel. Estes esquemas são mapeados em modelos de simulação baseados em OFDMA e são completamente simulados em CoCentric System Studio.
Os resultados obtidos com os modelos desenvolvidos mostram que os esquemas
de diversidade cooperativa atenuam os efeitos do desvanecimento induzido pela propagação multipercurso, aumentando desta forma a capacidade e cobertura dos sistemas wireless. Os ganhos são particularmente altos quando as perdas de percurso são consideráveis, como é o caso das zonas urbanas densas.
ABSTRACT: This dissertation is inserted into the wireless communication, or more specifically, into the cooperative diversity field.
within this thesis, the performance of low-complexity cooperative diversity schemes projected for mobile communication systems are studied, implemented and evaluated.
These schemes are mapped into simulation models based on OFDMA and are fully simulated in the CoCentric System Studio environment. The obtained results show that the proposed cooperative schemes for the uplink communication
mitigate fading induced by multipath propagation, thereby increasing the capacity and coverage of wireless systems. Cooperation gains are particularly high when multipath losses are considerable, as is the case for dense urban regions
Radio Resource Management Optimization For Next Generation Wireless Networks
The prominent versatility of today’s mobile broadband services and the rapid advancements in the cellular phones industry have led to a tremendous expansion in the wireless market volume. Despite the continuous progress in the radio-access technologies to cope with that expansion, many challenges still remain that need to be addressed by both the research and industrial sectors. One of the many remaining challenges is the efficient allocation and management of wireless network resources when using the latest cellular radio technologies (e.g., 4G). The importance of the problem stems from the scarcity of the wireless spectral resources, the large number of users sharing these resources, the dynamic behavior of generated traffic, and the stochastic nature of wireless channels. These limitations are further tightened as the provider’s commitment to high quality-of-service (QoS) levels especially data rate, delay and delay jitter besides the system’s spectral and energy efficiencies. In this dissertation, we strive to solve this problem by presenting novel cross-layer resource allocation schemes to address the efficient utilization of available resources versus QoS challenges using various optimization techniques. The main objective of this dissertation is to propose a new predictive resource allocation methodology using an agile ray tracing (RT) channel prediction approach. It is divided into two parts. The first part deals with the theoretical and implementational aspects of the ray tracing prediction model, and its validation. In the second part, a novel RT-based scheduling system within the evolving cloud radio access network (C-RAN) architecture is proposed. The impact of the proposed model on addressing the long term evolution (LTE) network limitations is then rigorously investigated in the form of optimization problems. The main contributions of this dissertation encompass the design of several heuristic solutions based on our novel RT-based scheduling model, developed to meet the aforementioned objectives while considering the co-existing limitations in the context of LTE networks. Both analytical and numerical methods are used within this thesis framework. Theoretical results are validated with numerical simulations. The obtained results demonstrate the effectiveness of our proposed solutions to meet the objectives subject to limitations and constraints compared to other published works
Técnicas de processamento com múltiplas antenas para o sistema LTE
Mestrado em Engenharia Electrónica e TelecomunicaçõesPerformance, mobilidade e partilha podem ser consideras como as três
palavras-chave nas comunicações móveis de hoje em dia. Uma das necessidades
fundamentais do ser humano é a partilha de experiencias e informação.
Com a evolução ao nível do hardware móvel, a crescente popularidade de
smartphones, tablets e outros dispositivos moveis, fez com que a exigência
em termos de capacidade e taxa de transferência por parte das redes móveis
não parasse de crescer.
As limitações das redes 3G fizeram com que não conseguissem corresponder
a tais exigências e como tal, a transição para uma tecnologia mais robusta e
eficiente passou a ser inevitável. A resposta escolhida como solução a longo
prazo é a rede designada por LTE, desenvolvida pela organização 3GPP é
assumido que será a rede de telecomunicações predominante no futuro. As
vantagens mais sonantes são, naturalmente, elevadas taxas de transmissão,
maior eficiência espectral, redução da latência e de custos de operação. As
principais tecnologias em que o LTE se baseia, são o OFDM e sua variante
para múltiplo acesso, OFDMA, usado para o downlink e o SC-FDMA para
o uplink. Além disso, usa sistemas com múltiplas antenas para impulsionar
a eficiência espectral. Apesar de já implementado em alguns países por
diversas operadoras, constantes pesquisas continuam a ser realizadas com
o intuito de melhorar a sua performance.
Nesta dissertação é proposto um esquema duplo de codificação na frequência
e no espaço (D-SFBC) para um cenário baseado em OFDM com 4
antenas de transmissão e duas antenas de recepção (4 × 2 D-SFBC) para
o downlink. No cenário considerado, 4 símbolos de dados são transmitidos
utilizando unicamente 2 sub-portadoras, fazendo com que, este sistema seja
limitado pela interferência. Para de forma eficiente descodificar os símbolos
de dados transmitidos, foi desenvolvido um equalizador iterativo no domínio
da frequência. Duas abordagens são consideradas: cancelamento da interferência
em paralelo (PIC) e sucessivo cancelamento de interferência (SIC).
Uma vez que apenas 2 sub-portadoras são usadas para transmitir quatro
símbolos de dados em paralelo, o esquema desenvolvido duplica a taxa de
dados quando comparado com o esquema 2 × 2 SFBC, especificado no
standard do LTE.
Os esquemas desenvolvidos foram avaliados sob as especificações para LTE
e usando codificação de canal. Os resultados mostram que os esquemas
implementados neste trabalho utilizando um equalizador iterativo supera os
convencionais equalizadores lineares na eliminação da interferência adicional
introduzida, em apenas 2 ou 3 iterações.Performance, mobility and sharing can be assumed as the three keywords
in the mobile communications nowadays. One of the fundamental needs of
human beings is to share experiences and information. With the evolution of
mobile hardware level, the growing popularity of smartphones, tablets and
other mobile devices, has made that the demand in terms of capacity and
throughput by mobile networks did not stop growing.
Thus, the limitations of 3G stops it of being the answer of such demand, and
a transition to a powerful technology has become unavoidable. The answer
chosen is LTE, developed by the 3GPP organization is assumed to be the
predominant telecommunications network in the future. The most relevant
advantages are high transmission rates, higher spectral efficiency, reducing
latency and operating costs. The key technologies in which LTE is based,
are OFDM and its variant schemes for multiple access, OFDMA, used for
downlink, and SC-FDMA for the uplink. It also uses multiple antennas systems
in order to improve spectral efficiency. Although already implemented
in some countries by several operators, continuous research is conducted in
order to improve their performance.
In this dissertation it is proposed a double space-frequency block coding
(D-SFBC) scheme for an OFDM based scenario with 4 transmit antennas
and 2 receive antennas (4×2 D-SFBC) for the downlink. In the considered
scenario, 4 data symbols are transmitted by using only 2 subcarriers and thus
the system is interference limited. To efficiently decode the transmitted data
symbols an iterative equalizer designed in frequency domain is developed.
Two approaches are considered: parallel interference cancellation (PIC) and
successive interference cancellation (SIC). Since only 2 subcarriers are used
to transmit 4 data symbols in parallel the developed scheme achieve the
double data rate when compared with the 2×2 SFBC, specified in the LTE
standard.
The developed schemes were evaluated under the main LTE specifications
and using channel coding. The results have show that the schemes implemented
in this work using an interactive equalizer outperforms the conventional
linear equalizers in the interference removal, just by using 2 or 3
iterations
- …