Nowadays, Opportunistic Routing (OR) is widely considered to be the most important paradigm for Multi-hop wireless networks (MWNs). It exploits the broadcast nature of wireless medium to propagate information from one point to another within the network. In OR scheme, when a node has new information to share, it rst needs to set its forwarding list which include the IDs and/or any relevant information to its best suited neighboring nodes. This operation is supported by the use of appropriate metrics. Then, it executes a coordination algorithm allowing transmission reliability and high throughput among the next-hop forwarders. In this paper, we provide a comprehensive guide to understand the characteristics and challenges faced in the area of opportunistic routing protocols in MWNs. Moreover, since the planet we live on is largely covered by water, OR protocols have gained much attention during the last decade in real-time aquatic applications, such as oil/chemical spill monitoring, ocean resource management, anti-submarine missions and so on. One of the major problems in Underwater Wireless Sensor Network (UWSNs) is determining an e cient and reliable routing methodology between the source node and the destination node. Therefore, designing e cient and robust routing protocols for UWSNs became an attractive topic for researchers. This paper seeks to address in detail the key factors of underwater sensor network. Furthermore, it calls into question 5 state-of-the-art routing protocols proposed for UWSN: The Depth-Based Routing protocol (DBR), the Energy-E cient Depth-Based Routing protocol (EEDBR), the Hydraulic-pressure-based anycast routing protocol (Hydrocast), the Geographic and opportunistic routing protocol with Depth Adjustment for mobile underwater sensor networks (GEDAR), and the Void- Aware Pressure Routing for underwater sensor networks (VAPR). Finally, it covers the performance of those protocol through the use of the R programming language.

A utilização das redes sem fio nos mais diversos segmentos vem crescendo vertiginosamente nos últimos anos. Aliado ao crescimento da utilização das redes, está a diversificação de aplicações utilizadas por todos os usuários, sejam eles corporativos ou domésticos. Isto tem contribuído significativamente para o desenvolvimento de tecnologias que ofereçam mecanismos de qualidade de serviço, de forma a permitir o uso satisfatório de aplicações como voz e vídeo em tempo real. Este trabalho estuda os efeitos que a existência de tráfego de voz e dados em redes sem fio padrão IEEE 802.11 causa no desempenho da rede e por consequência no desempenho das aplicações. Para realizar este estudo foram executadas simulações baseadas em uma rede sem fio com topologia ad hoc, com variações no número de estações e quantidade de tráfego gerado. Foram simulados os padrões 802.11g e 802.11e com o objetivo de analisar o desempenho dos mecanismos de qualidade de serviço e os benefícios que estes mecanismos geram para a transmissão de tráfego em tempo real em redes sem fio padrão IEEE 802.11. Verificou-se que o padrão IEEE 802.11e apresenta um ganho de desempenho para aplicações de tempo real, porém ele apresenta limitações que devem ser consideradas nos projetos de redes sem fio. / The use of wirelles networks in most various sectors has been growing drastically in past years Allied to the wireless networks use, the diversification of applications and services provided can be directly verified whether by home or corporate users. This alliance contributes significantly to the needs of technology development which offer the quality of service mechanisms, allowing satisfactory use of real-time applications like voice and video This paper studies the effects that coexistent voice and data traffic on a IEEE 802.11 standard wireless network cause in the network performance and, consequently, in the applications performance. To make this study a reality, it was necessary to run simulations of a wireless ad hoc topology network, with variations in the number of workstations and the quantity of generated traffic. The 802.11g and 802.11e standards were used in the simulations with the purpose of analyzing the performance of quality of service mechanisms and the benefits they create for the real-time transmissions in IEEE 802.11 standard wireless networks. It was verified that the IEEE 802.11e standard presents a perfomance gain for the real-time applications, but it has limitations that should be considered in wireless networks design.

A utilização das redes sem fio nos mais diversos segmentos vem crescendo vertiginosamente nos últimos anos. Aliado ao crescimento da utilização das redes, está a diversificação de aplicações utilizadas por todos os usuários, sejam eles corporativos ou domésticos. Isto tem contribuído significativamente para o desenvolvimento de tecnologias que ofereçam mecanismos de qualidade de serviço, de forma a permitir o uso satisfatório de aplicações como voz e vídeo em tempo real. Este trabalho estuda os efeitos que a existência de tráfego de voz e dados em redes sem fio padrão IEEE 802.11 causa no desempenho da rede e por consequência no desempenho das aplicações. Para realizar este estudo foram executadas simulações baseadas em uma rede sem fio com topologia ad hoc, com variações no número de estações e quantidade de tráfego gerado. Foram simulados os padrões 802.11g e 802.11e com o objetivo de analisar o desempenho dos mecanismos de qualidade de serviço e os benefícios que estes mecanismos geram para a transmissão de tráfego em tempo real em redes sem fio padrão IEEE 802.11. Verificou-se que o padrão IEEE 802.11e apresenta um ganho de desempenho para aplicações de tempo real, porém ele apresenta limitações que devem ser consideradas nos projetos de redes sem fio. / The use of wirelles networks in most various sectors has been growing drastically in past years Allied to the wireless networks use, the diversification of applications and services provided can be directly verified whether by home or corporate users. This alliance contributes significantly to the needs of technology development which offer the quality of service mechanisms, allowing satisfactory use of real-time applications like voice and video This paper studies the effects that coexistent voice and data traffic on a IEEE 802.11 standard wireless network cause in the network performance and, consequently, in the applications performance. To make this study a reality, it was necessary to run simulations of a wireless ad hoc topology network, with variations in the number of workstations and the quantity of generated traffic. The 802.11g and 802.11e standards were used in the simulations with the purpose of analyzing the performance of quality of service mechanisms and the benefits they create for the real-time transmissions in IEEE 802.11 standard wireless networks. It was verified that the IEEE 802.11e standard presents a perfomance gain for the real-time applications, but it has limitations that should be considered in wireless networks design.

The increasing popularity of wireless networks over the last years indicates that there will be a demand for communicating devices providing high capacity communication together with QoS requirements. There are two types of wireless networks, infrastructure and Ad Hoc networks. The variation of topology caused by the mobility of hosts in the Ad Hoc networks results in a long latency, large jitter and low throughput. In infrastructure wireless networks, a base station (BS) or an Access Point (AP) is in charge of the data transmission. Therefore, the wireless hop can be considered as another hop of the transmission path. With the rapid growth of wireless traffics, the future wireless network is expected to provide services for heterogeneous data traffics with different quality of service requirements. Most proposed schemes do not have mechanisms to adapt to environment changes. In real situation, bandwidths, error rates, and loss rates of wireless links vary frequently. The QoS issues are very important in modern networks. There are many proposed service models and mechanisms to support QoS in wireline networks. Most of these QoS mechanisms are not suitable for direct application to the wireless network because of the characteristics of wireless communication which includes: 1) high error rates and bursty errors, 2) location-dependent and time-varying wireless channel capacity, 3) scarce bandwidth, 4) user mobility, and 5) power constraints of the mobile hosts. All of these above characteristics make the development of QoS in wireless networks very difficult and challenging. We try to cope with the bandwidth variations caused by the high error rate and bursty errors in wireless links, and the location-dependent and time-varying natures of wireless channel capacity. Furthermore, we expect to utilize the scarce wireless bandwidth more efficiently. In our proposed scheme, the higher priority flow is capable of broadcasting a message to inform the lower priority flows to change their priorities to adapt to environment variations. We will base on the differentiated service model and propose a Wireless Differentiation (WD) scheme for UDP flows and a Wireless Differentiation with Prioritized ACK (WDPA) scheme for connections with TCP flows which provide QoS support for IEEE 802.11b and do not change the basic access mechanism of IEEE 802.11b.

The purpose of this reasearch was to develop a respiratory monitoring system using a reflective object sensor based belt to measure the thoracic expansion of a neonatal for future application at the medical center of the Universidad Evangelica Boliviana (UEB). This medical center, being founded by the UEB University, is dedicated to help and serve the poor and currently has no respiratory monitoring system. The methodology used was first to build and test the respiratory sensor belt and test the relationship between the blet expansion and the voltage generated. The, to incorporate the respiratory sensor belt in a system that would allow individual testing as well as group testing in a wireless network. The system was simulated using an expandable plastic container that was expanded and extracted periodically, registering the results in a MATLAB software. The system gave successful results and generated the frequency results of each cycle, average frequency and deviation frequency. The system demonstrated to be reliable and to have repeatable results.

Ο σκοπός της μεταπτυχιακής εργασίας, ήταν η ανάλυση, όσον αφορά την πιθανότητα σφάλματος, ενός τηλεπικοινωνιακού συστήματος το οποίο μεταδίδει ιατρική πληροφορία, ασύρματα, μεταξύ δυο κόμβων ενός δικτύου ιατρικών αισθητήρων. Το δίκτυο αυτό περιλαμβάνει έναν επιβλέποντα κόμβο ο οποίος προωθεί, τα δεδομένα που συλλέχθηκαν, σε ένα σταθμό βάσης, ο οποίος βρίσκεται σε ένα νοσοκομείο. Η μετάδοση της ιατρικής πληροφορίας επιτυγχάνεται με ένα πομποδέκτη ο οποίος είναι ενσωματωμένος σε όλους τους κόμβους του ασύρματου δικτύου. Χρησιμοποιείται ο ΧΕ1209 πομποδέκτης της εταιρίας Xemics S.A. ο οποίος χρησιμοποιεί την διαμόρφωση 2-CPFSK ενώ η φέρουσα συχνότητα είναι τα 36,86 kHz. Προτού, μεταδοθεί η ιατρική πληροφορία, γίνεται μια κατάλληλη επεξεργασία ώστε να προστατευθεί από τον πανταχού παρών θόρυβο και να φτάσει αναλλοίωτη στο δέκτη. Η επεξεργασία της ιατρικής πληροφορίας περιλαμβάνει τον κυκλικό έλεγχο πλεονασμού (Cyclic Redundancy Check - CRC) και την εφαρμογή ενός σχήματος διόρθωσης λαθών (Forward Error Correction – FEC). / The purpose of my master thesis was, the analysis, concerning the probability of error, of a telecommunication system, which transmits medical information, wireless, from one node, of a medical sensor network, to another. This network consists of a supervising node, who forwards the collected data, to a base station, which resides in a hospital. The transmission of the medical information is achieved by a transmitter embedded to all the nodes of the wireless network. We have used the ΧΕ1209 transmitter of Xemics S.A., who uses the 2-CPFSK modulation, whilst the carrier frequency is 36.86 kHz. Before the transmission of the medical information takes place, the data undergo a processing phase, in order to be protected from the ubiquitous noise, and reach the receiver intact. The processing of the medical information includes the Cyclic Redundancy Check (CRC) and the application of a form of error correction called Forward Error Correction (FEC).

Pagrindiniu įmonės tikslu laikomas įmonės vertės didinimas gali būti realizuojamas plečiant rinkos dalį, didinat parduodamų prekių ar paslaugų kiekį, taip pat didinant darbo organizavimo efektyvumą įmonėje. Vienas iš efektyvumo didinimo įmonėje sprendimų yra bevielio kompiuterių tinklo įmonėje diegimas. Naudojant bevielį kompiuterių tinklą pasiekiamas didesnis personalo mobilumas ir darbo efektyvumas, kai reikiamą informaciją darbuotojas gali gauti būdamas bet kurioje įmonės vietoje. Darbe atlikta bevielio tinklo diegimo metodų teorinė analizė, pasiūloma bevielio tinklo diegimo vertinimo metodika ir atliekamas metodikos taikymo tyrimas.Darbe pateikiama bevielio tinklo diegimo įmonėje metodika leidžia apskaičiuoti mobilumo naudą įmonei per papildomos vert���s sukūrimą ir kaštų sumažinimą, bei parinkti tinkamą bevielio tinklo architektūros ir saugumo sprendimus, atsižvelgiant į įmonės poreikius. Pristatomas modelis, leidžiantis įvertinti bevielio tinklo teikiamą naudą įmonėje. Bevielio kompiuterių tinklo architektūrinių sprendimų pritaikymo įmonei metodika formuluojama, remiantis atliktų eksperimentinių tyrimų rezultatais. / The main goal for a company is to increase its value which can be achieved by expanding the market share, increasing sales volume of its goods and services, improving labour productivity. One of the improvements aiming at achieving labour productivity is the implementation of wireless computer network. The use of wireless computer network gives a higher degree of mobility and efficiency for staff within the company, in particular when employee needs to access the information from any place in the territory of a company. This work contains from performed theoretic analysis of implementation methods of wireless network, the suggested methodology of Wireless Network evaluation and performed investigation of realised methodology of Wireless Network implementation in the company. The paper presents the methodology of wireless networks implementation in a company, evaluates the efficiency of wireless networks and suggests the possible architectural and security solutions for wireless networks implementation. Further more, the presented methodology enables to evaluate the benefits of mobility, in particular for added value creation and costs reduction, and allows choosing the appropriate architectural and security solutions of wireless computer network. The presented methodology is based on the results of experimental research.

Wireless Sensor Network (WSN) is an emerging multi-hop wireless network technology, and the greenhouse network monitoring system is one of the key applications of WSNs in which various parameters such as temperature, humidity, pressure and power can be monitored. Here, we aim to study the performance of a simulation-based greenhouse monitoring system. To design the greenhouse monitoring system based on WSN, we have used ZigBee-based devices (end devices, routers, coordinators, and actuators. Our proposed greenhouse monitoring network has been designed and simulated using the network simulator OPNET Modeller.The investigation is split into two; first, the aim is to find the optimal Transmit (Tx) power set out at sensor nodes and second, the focus is on studying how increasing the number of sensor nodes in the same greenhouse network will affect the overall network performance. ZigBee-based greenhouses corresponded to 4 network scenarios and are simulated using OPNET Modeller in which 22 different transmit (Tx) power (22 cases) in Scenario 1 is simulated, scenario 2, 3 and 4 estimated to 63, 126, 189 number of sensor nodes respectively. Investigating the performance of the greenhouse monitoring network performance metrics such as network load, throughput, packets sent/received and packets loss are considered to be evaluated under varied transmit (Tx) power and increasing number of sensor nodes. Out of the comprehensive studies concerning simulation results for 22 different transmit (Tx) power cases underlying the greenhouse monitoring network (Scenario1), it is found that packets sent/received and packets loss perform the best with the transmitted (Tx) power falling in a range of 0.9 mWatt to 1.0 mWatt while packet sent/received and packet loss are found to perform moderately with the transmitted (Tx) power values that lie in a range of 0.05 mWatt to 0.8 mWatt. Less than 0.05 mWatt and greater than 0.01 microWatt Tx power experience, the worst performance in terms of particularly packet dropped case. For instance, in the case of the packet dropped (not joined packet, i.e., generated at the application layer but not able to join the network due to lack of Tx power), with a Tx power of 0.01 mWatt, 384 packets dropped with a Tx power of 0.02 and 0.03 mWatt, 366 packets dropped, and with a Tx power of 0.04 and 0.05, 336 packet dropped.While increasing the number of sensor nodes, as in scenario 2, 3 and 4, dealing with sensor nodes 63, 126 and 189 correspondingly, the MAC load, MAC throughput, packet sent/received in scenario 2 are found to perform better than that of scenario 3 and scenario 4, while packet loss in scenarios 2, 3 and 4 appeared to be 15%, 12% and 83% correspondingly.

In this work, we focus on securing communication over wireless data networks from malicious eavesdroppers, using smart antennas. While conventional cryptography based approaches focus on hiding the meaning of the information being communicated from the eavesdropper, we consider a complimentary class of strategies that limit knowledge of the existence of the information from the eavesdropper. We profile the performance achievable using simple beamforming strategies using a newly defined metric called exposure region. We then present three strategies within the context of an approach called 'virtual arrays of physical arrays' to significantly improve the exposure region performance of a wireless LAN environment. Using simulations, analysis, and field experiments, we validate and evaluate the proposed strategies.

The growth of interactive multimedia (IMM) applications is one of the major driving forces behind the swift evolution of next-generation wireless networks where the traffic is expected to be varying and widely diversified. The amalgamation of multimedia applications on high-speed wireless networks is somewhat a natural evolution. Wireless local area network (WLAN) was initially developed to carry non-real time data. Since this type of traffic is bursty in nature, the channel access schemes were based on contention. However real time traffic (e.g. voice, video and other IMM applications) are different from this traditional data traffic as they have stringent constraints on quality of service (QoS) metrics like delay, jitter and throughput. Employing contention free channel access schemes that are implemented on the point coordination function (PCF), as opposed to the numerous works on the contending access schemes, is the plausible and intuitive approach to accommodate these innate requirements. Published researches show that works have been done on improving the distributed coordination function (DCF) to handle IMM traffic. Since the WLAN traffic today is a mix of both, it is only natural to utilize both, DCF and PCF, in a balanced manner to leverage the inherent strengths of each of them. We saw a scope in this technique and develop a scheme that combines both contention and non-contention based phases to handle heterogeneous traffic in WLAN. Standard access scheme, like 802.11e, improves DCF functionality by trying to emulate the functions of PCF. Researchers have made a multitude of improvements on 802.11e to reduce the costs of implementing the scheme on WLAN. We explore improving the PCF, instead, as this is more stable and implementations would be less costly. The initial part of this research investigates the effectiveness of the point coordination function (PCF) for carrying interactive multimedia traffic in WLAN. The performance statistics of IMM traffic were gathered and analyzed. Our results showed that PCF-based setup for IMM traffic is most suitable for high load scenarios. We confirmed that there is a scope in improving IMM transmissions on WLAN by using the PCF. This is supported by published researches on PCF related schemes in carrying IMM traffic on WLAN. Further investigations, via simulations, revealed that partitioning the superframe (SF) duration according to the need of the IMM traffic has considerable impact on the QoS of the WLAN. A theoretical model has been developed to model the two phases, i.e., PCF and DCF, of WLAN medium access control (MAC). With this model an optimum value of the contention free period (CFP) was calculated to meet the QoS requirement of IMM traffic being transmitted. Treating IMM traffic as data traffic or equating both IMM and non-IMM together could compromise a fair treatment that should be given to these QoS sensitive traffic. A self-adaptive scheme, called MAC with Dynamic Superframe Selection (MDSS) scheme, generates an optimum SF configuration according to the QoS requirements of traversing IMM traffic. That particular scheme is shown to provide a more efficient transmission on WLAN. MDSS maximizes the utilization of CFP while providing fairness to contention period (CP). The performance of MDSS is compared to that of 802.11e, which is taken as the benchmark for comparison. Jitter and delay result for MDSS is relatively lower while throughput is higher. This confirms that MDSS is capable of making significant improvement to the standard access scheme.