[pt] Existe um crescente interesse na introdução de serviços integrados no ambiente de comunicações móveis e sem fio. Estes serviços podem incluir, em alguns casos, informação na forma de áudio, vídeo, imagens e dados simultaneamente junto com o serviço existente de voz nas redes celulares. Devido à necessidade por maior faixa, o aumento da capacidade da interface rádio continuará sendo um dos principais requisitos para a introdução destes novos serviços. Para atender esta necessidade, vários métodos de acesso estão sendo propostos. Esta tese propõe um novo protocolo de acesso, D-RAMA, que visa extender os métodos de acesso determinísticos TRAMA e FRAMA. A validação do algoritmo é feita por meio de simulação considerando diversas interfaces rádio, assim como diferentes tipos de tráfegos. / [en] Third generation systems will present several new enhancements while compared with current second generation technologies. Some of the most important ones are the support of integrated services (audio, video, data) as well as speech, operation in different radio environments with several propagation conditions and increased capacity. These features demand an efficient media access control (MAC) protocol, supporting both Constant Bit Rate (CBR) and Variable Bit Rate (VBR) traffic types with different Quality of Service (QoS) requeriments. In order to supply this demand, several packet access methods are being proposed. This thesis presents a new media access protocol, D-RAMA (Dynamic Priorities Resource Auction Multiple Access) and FRAMA (Fair resource Auction Multiple Access) methods, and is designed to fulfill the requirements of third generation systems. The protocol is validated through simulations, considering several radio interfaces and traffic sources.

The dissertation thesis is focused on analysis, modeling and optimization of the medium access layer of power line communication. In the first part of the paper, the thesis briefly summarizes a basic information of power line communication. In the next sections, the objectives of the dissertation are placed. A simplification of current models of HomePlug and a optimalization of distribution function in back off procedure are one of the main goals of this work. A detailed analysis of HomePlug technology, which is widespread used in the broadband transmission, follows. The work is focused on analyzing of the MAC layer in this part. The discrete simulation models have been implemented in Matlab. The approximation discrete numerical model has been used for analysis of various distribution functions for HomePlug to optimalize backoff algorithm. The new optimalizations are suitable for large networks. The new approach of MAC modelling is introduced in last part of this work. The new model is not exact as Markov models but it is faster and easier for implementation. The analytical model desribes a system using probabilistic functions.

This work starts from the proposition that it is beneficial to conserve communication energy in Wireless Sensor Networks (WSNs). For WSNs there is an added incentive for energy-efficient communication. The power supply of a sensor is often finite and small. Replenishing the power may be impractical and is likely to be costly. Wireless Sensor Networks are an important area of research. Data about the physical environment may be collected from hostile or friendly environments. Data is then transmitted to a destination without the need for communication cables. There are power and resource constraints upon WSNs, in addition WSN networks are often application specific. Different applications will often have different requirements. Further, WSNs are a shared medium system. The features of the MAC (Medium Access Control) protocol together with the application behaviour shape the communication states of the node. As each of these states have different power requirements the MAC protocol impacts upon the operation and power consumption efficiency. This work focuses on the development of an energy conservation protocol for WSNs where direct communication between sources and a base station is feasible. Whilst the multi-hop approach has been regarded as the underlying communication paradigm in WSNs, there are some scenarios where direct communication is applicable and a significant amount of communication energy can be saved. The Power & Reliability Aware Protocol has been developed. Its main objectives are to provide efficient data communication by means of energy conservation without sacrificing required reliability. This has been achieved by using direct communication, adaptive power adaptation and intelligent scheduling. The results of simulations illustrate the significance of communication energy and adaptive transmission. The relationship between Received Signal Strength Indicator (RSSI) and Packet Reception Rate (PRR) metrics is established and used to identify when power adaptation is required. The experimental results demonstrate an optimal region where lower power can be used without further reduction in the PRR. Communication delays depend upon the packet size whilst two-way propagation delay is very small. Accurate scheduling is achieved through monitoring the clock drift. A set of experiments were carried out to study benefits of direct vs. multi-hop communication. Significant transmitting current can be conserved if the direct communication is used. PoRAP is compared to Sensor-MAC (S-MAC), Berkeley-MAC (B-MAC) and Carrier Sense Multiple Access (CSMA). Parameter settings used in the Great Duck Island (GDI) a production habitat monitoring WSNs were applied. PoRAP consumes the least amount of energy.

<p>Over years<strong>,</strong> there have been tremendous changes in internetworking technologies and there are a number of real time applications that are flooded into the market. Most real-time applications are sensitive to traffic loss because of their nature of exchanging data without acknowledgement. In any type of data network, redundancy is important to backup and recover the connectivity without human intervention in case of device or link failure. However, it is very crucial to design an optimal redundant network, particularly for real-time applications providing minimal losses during fail-over. Configuration of redundancy in different networks varies and depends on the equipment and network design itself.</p><p>This thesis focuses on the redundancy needed in campus network design which is quite popular nowadays in most of medium and large enterprises, universities or government agencies. Two major designs of redundancy are studied: default gateway redundancy and routed access. In the first option<strong>,</strong> the one logical segment of network uses common L2 switches while in the other – the same segment is constructed with more expensive advanced multilayer switches. The network is built in the lab environment. As an example of real-time communication the VoIP call is simulated in the network. The failures on different areas of nodes or links are caused manually. Results of packet loss during fail-over are recorded. The baseline of recovery performance is constructed using these results which are derived from different scenarios using different configurations and equipment. The baseline data is evaluated and conclusion is made on the trade-offs, limitations, advantages and disadvantages of the redundancy options in the campus network design.</p><p>The work done in this thesis is supportive for network architects and designers to take into consideration the equipment and configuration to be used when implementing redundancy for real-time communications. The results and conclusion will support them in choosing the options for constructing the redundant network<strong>,</strong> or taking into account the trade-offs when migrating from one option to another.</p>

Over years, there have been tremendous changes in internetworking technologies and there are a number of real time applications that are flooded into the market. Most real-time applications are sensitive to traffic loss because of their nature of exchanging data without acknowledgement. In any type of data network, redundancy is important to backup and recover the connectivity without human intervention in case of device or link failure. However, it is very crucial to design an optimal redundant network, particularly for real-time applications providing minimal losses during fail-over. Configuration of redundancy in different networks varies and depends on the equipment and network design itself. This thesis focuses on the redundancy needed in campus network design which is quite popular nowadays in most of medium and large enterprises, universities or government agencies. Two major designs of redundancy are studied: default gateway redundancy and routed access. In the first option, the one logical segment of network uses common L2 switches while in the other – the same segment is constructed with more expensive advanced multilayer switches. The network is built in the lab environment. As an example of real-time communication the VoIP call is simulated in the network. The failures on different areas of nodes or links are caused manually. Results of packet loss during fail-over are recorded. The baseline of recovery performance is constructed using these results which are derived from different scenarios using different configurations and equipment. The baseline data is evaluated and conclusion is made on the trade-offs, limitations, advantages and disadvantages of the redundancy options in the campus network design. The work done in this thesis is supportive for network architects and designers to take into consideration the equipment and configuration to be used when implementing redundancy for real-time communications. The results and conclusion will support them in choosing the options for constructing the redundant network, or taking into account the trade-offs when migrating from one option to another.

The purpose of this master’s thesis is foremost to provide a simple guide how to build elements of optical metropolitan area network. The basic model consists to sequence of construction, network topology, passive and active parts. The collection contains examples of alternative technology such as Wireless LAN with different frequency. The optical network construction based on optical cable, fibres, splices, trays, adapters, connectors and active parts for example a lot of media convertor models. After that there are demonstrating type of wavelength division multiplexer used in metropolitan area network – passive planar PCL splitter. One of the passive planar splitter are used to increase optical fibre channel. At the end of the collection a simplified examples of used measurements – optical time domain reflectometry and optical fibre transmission. Contains standard protocols or reflectogram. The conclusion of this thesis summarizes costs of FTTb (Fibre To The Building) model of optical metropolitan area network in Czech republic and future contribution for society.