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Thesis--Greifswald, 1894. / Lebenslauf. Bibliography, p. v-vi.

<p>In order to ensure the successful demonstration that the Weather Message switching center Replacement (WMSCR) of the Federal Aviation Administration (FAA) can complete its primary mission of accepting and distributing various data formats in use today and those of future systems, including the expected message traffic, this study was initiated.</p> <p> This Test Data set Formulation will specify the various data formats, worst-case traffic load/size, and a distribution scenario for the WMSCR. From this Formulation, an actual Test Data Set can be constructed and used to test the WMSCR.</p> <p> A description of the WMSCR, its operational environment, current users, future users, various message formats and associated sizing requirements per interface are detailed within.</p> / Master of Engineering

Development of Wireless Sensor Nodes revolutionaries sensing and control application. The size of sensor node makes it ideal to be used in variety of applications, but this brings more challenges and problems especially as the capacity of onboard battery is limited. It is due to the very reason that initial research in the field of WSN especially on MAC targets mainly on the energy conservation and gives secondary importance towards other attributes of MAC protocols. These attributes includes latency, throughput, fairness and collision. This research keeping in view of current application requirements which demands QoS as well as energy conservation in static and mobile sensor networks proposes MAC protocols to meet these challenges. In this research to improve the efficiency of the collision resolution algorithms used in mainly contention based MAC protocols, an Improved Binary Exponential Backoff Algorithm is proposed. The main target of this protocol is to resolve the problem of access collision by employing interim backoff period. The protocol targets to improve upon the performance of conventional Binary Exponential Backoff Algorithm which suffers heavily from collision. The result shows significant reduction in collision which increases the efficiency of the network in terms of QoS and energy conservation. To eliminate the problem of collision which is one of the major sources of network performance degradation a novel Delay Controlled Collision Free contention based MAC is designed. The protocol uses novel delay allocation technique. DCCF also provides mechanism to achieve fairness among the nodes. Detailed analysis and comparative result shows substantial increase in throughput and decrease in latency as compared to Industrial standard of IEEE 802.15.4 CSMA/CA MAC. The research also proposed novel MAC protocols for mobile sensor networks. These protocols uses a methodology which is based upon signal strength of the beacon sent to the node from various neighbouring coordinators that enable the nodes to seamlessly enter from one cluster to another without any link loss and unnecessary delays in the shape of association. The proposed scheme is implemented over IEEE 802.15.4 enabling the standard to perform better with dynamic topology. Result shows that mobility adaptive 802.15.4 protocol shows improvement in QoS and conserve energy far better than the existing conventional CSMA/CA MAC standard. Also the algorithm is implemented over Delay Controlled Collision Free Mac protocol and a detail comparison is carried out with other mobility adaptive MAC protocols. The result shows significant decrease in latency as well as high gain in throughput and considerable reduction in energy as compared to the mobility adaptive MAC protocols. Finally in order to resolve fundamental problem of scalable network which suffers from bottleneck as more nodes in the last hop tries to send data towards the sink, a novel protocol is proposed which allows more than one node at a time to transmit the data towards the sink. The protocol named Simultaneous Multi node CSMA/CA enables the conventional industrial standard of IEEE 802.15.4 CSMA/CA protocol to allow more than one node to transmit the data towards the coordinator or sink node. The protocol out performs the existing standard and provides significant increase in QoS of the network.

The aim of this project is to address the challenges associated with extending the radio frequency capability of Electric Potential Sensors to greater than 10 MHz. This has culminated in a single broadband sensor, with a frequency range of 200 Hz to greater than 200 MHz. The use of Electric Potential Sensors for the measurement of electric field with minimal perturbation has already been demonstrated at Sussex. These high impedance sensors have been successfully employed in measuring signals with frequencies in the range 1 mHz to 2 MHz. Many different versions of these sensors have been produced to cater for specific measurement requirements in a wide variety of experimental situations. From the point of view of this project, the relevant prior work is the acquisition of a 2 MHz electric field nuclear magnetic resonance signal, and the non-destructive testing of composite materials at audio frequency. Two very distinct electric field measurement scenarios are described which illustrate the diverse capabilities of the broadband sensor. Firstly, an electric field readout system for nuclear quadrupole resonance is demonstrated for the first time, with a sodium chlorate sample at a frequency of 30 MHz. Nuclear quadrupole resonance is an important technique with applications in the detection of explosives and narcotics. Unlike nuclear magnetic resonance a large magnet is not required, opening up the possibility of portable equipment. The electric field readout system is shown to be simpler than the conventional magnetic readout and may therefore contribute to the development of portable devices. Secondly, a broadband, high spatial resolution microscope system for materials characterisation with four different imaging modes is described. This includes; the surface topography of a conducting sample; the dielectric constant variation in glass/epoxy composite; the conductivity variation in a carbon fibre composite; and the electrode pixels inside a solid state CMOS fingerprint sensor.

The thesis investigates new approaches to increase the user capacity and improve the error performance of Code Division Multiple Access (CDMA) by employing adaptive interference cancellation and collaborative spreading and space diversity techniques. Collaborative Coding Multiple Access (CCMA) is also investigated as a separate technique and combined with CDMA. The advantages and shortcomings of CDMA and CCMA are analysed and new techniques for both the uplink and downlink are proposed and evaluated. Multiple access interference (MAI) problem in the uplink of CDMA is investigated first. The practical issues of multiuser detection (MUD) techniques are reviewed and a novel blind adaptive approach to interference cancellation (IC) is proposed. It exploits the constant modulus (CM) property of digital signals to blindly suppress interference during the despreading process and obtain amplitude estimation with minimum mean squared error for use in cancellation stages. Two new blind adaptive receiver designs employing successive and parallel interference cancellation architectures using the CM algorithm (CMA) referred to as ‘CMA-SIC' and ‘BA-PIC', respectively, are presented. These techniques have shown to offer near single user performance for large number of users. It is shown to increase the user capacity by approximately two fold compared with conventional IC receivers. The spectral efficiency analysis of the techniques based on output signal-to interference-and-noise ratio (SINR) also shows significant gain in data rate. Furthermore, an effective and low complexity blind adaptive subcarrier combining (BASC) technique using a simple gradient descent based algorithm is proposed for Multicarrier-CDMA. It suppresses MAI without any knowledge of channel amplitudes and allows large number of users compared with equal gain and maximum ratio combining techniques normally used in practice. New user collaborative schemes are proposed and analysed theoretically and by simulations in different channel conditions to achieve spatial diversity for uplink of CCMA and CDMA. First, a simple transmitter diversity and its equivalent user collaborative diversity techniques for CCMA are designed and analysed. Next, a new user collaborative scheme with successive interference cancellation for uplink of CDMA referred to as collaborative SIC (C-SIC) is investigated to reduce MAI and achieve improved diversity. To further improve the performance of C-SIC under high system loading conditions, Collaborative Blind Adaptive SIC (C-BASIC) scheme is proposed. It is shown to minimize the residual MAI, leading to improved user capacity and a more robust system. It is known that collaborative diversity schemes incur loss in throughput due to the need of orthogonal time/frequency slots for relaying source's data. To address this problem, finally a novel near-unity-rate scheme also referred to as bandwidth efficient collaborative diversity (BECD) is proposed and evaluated for CDMA. Under this scheme, pairs of users share a single spreading sequence to exchange and forward their data employing a simple superposition or space-time encoding methods. At the receiver collaborative joint detection is performed to separate each paired users' data. It is shown that the scheme can achieve full diversity gain at no extra bandwidth as inter-user channel SNR becomes high. A novel approach of ‘User Collaboration' is introduced to increase the user capacity of CDMA for both the downlink and uplink. First, collaborative group spreading technique for the downlink of overloaded CDMA system is introduced. It allows the sharing of the same single spreading sequence for more than one user belonging to the same group. This technique is referred to as Collaborative Spreading CDMA downlink (CS-CDMA-DL). In this technique T-user collaborative coding is used for each group to form a composite codeword signal of the users and then a single orthogonal sequence is used for the group. At each user's receiver, decoding of composite codeword is carried out to extract the user's own information while maintaining a high SINR performance. To improve the bit error performance of CS-CDMA-DL in Rayleigh fading conditions, Collaborative Space-time Spreading (C-STS) technique is proposed by combining the collaborative coding multiple access and space-time coding principles. A new scheme for uplink of CDMA using the ‘User Collaboration' approach, referred to as CS-CDMA-UL is presented next. When users' channels are independent (uncorrelated), significantly higher user capacity can be achieved by grouping multiple users to share the same spreading sequence and performing MUD on per group basis followed by a low complexity ML decoding at the receiver. This approach has shown to support much higher number of users than the available sequences while also maintaining the low receiver complexity. For improved performance under highly correlated channel conditions, T-user collaborative coding is also investigated within the CS-CDMA-UL system.

One of the main issues involved in the development of future wireless communication systems is the multiple access technique used to efficiently share the available spectrum among users. In rich multipath environment, spatial dimension can be exploited to meet the increasing number of users and their demands without consuming extra bandwidth and power. Therefore, it is utilized in the multiple-input multiple-output (MIMO) technology to increase the spectral efficiency significantly. However, multiuser MIMO (MU-MIMO) systems are still challenging to be widely adopted in next generation standards. In this thesis, new techniques are proposed to increase the channel and user capacity and improve the error performance of MU-MIMO over Rayleigh fading channel environment. For realistic system design and performance evaluation, channel correlation is considered as one of the main channel impurities due its severe influence on capacity and reliability. Two simple methods called generalized successive coloring technique (GSCT) and generalized iterative coloring technique (GICT) are proposed for accurate generation of correlated Rayleigh fading channels (CRFC). They are designed to overcome the shortcomings of existing methods by avoiding factorization of desired covariance matrix of the Gaussian samples. The superiority of these techniques is demonstrated by extensive simulations of different practical system scenarios. To mitigate the effects of channel correlations, a novel constellation constrained MU-MIMO (CC-MU-MIMO) scheme is proposed using transmit signal design and maximum likelihood joint detection (MLJD) at the receiver. It is designed to maximize the channel capacity and error performance based on principles of maximizing the minimum Euclidean distance (dmin) of composite received signals. Two signal design methods named as unequal power allocation (UPA) and rotation constellation (RC) are utilized to resolve the detection ambiguity caused by correlation. Extensive analysis and simulations demonstrate the effectiveness of considered scheme compared with conventional MU-MIMO. Furthermore, significant gain in SNR is achieved particularly in moderate to high correlations which have direct impact to maintain high user capacity. A new efficient receive antenna selection (RAS) technique referred to as phase difference based selection (PDBS) is proposed for single and multiuser MIMO systems to maximize the capacity over CRFC. It utilizes the received signal constellation to select the subset of antennas with highest (dmin) constellations due to its direct impact on the capacity and BER performance. A low complexity algorithm is designed by employing the Euclidean norm of channel matrix rows with their corresponding phase differences. Capacity analysis and simulation results show that PDBS outperforms norm based selection (NBS) and near to optimal selection (OS) for all correlation and SNR values. This technique provides fast RAS to capture most of the gains promised by multiantenna systems over different channel conditions. Finally, novel group layered MU-MIMO (GL-MU-MIMO) scheme is introduced to exploit the available spectrum for higher user capacity with affordable complexity. It takes the advantages of spatial difference among users and power control at base station to increase the number of users beyond the available number of RF chains. It is achieved by dividing the users into two groups according to their received power, high power group (HPG) and low power group (LPG). Different configurations of low complexity group layered multiuser detection (GL-MUD) and group power allocation ratio (η) are utilized to provide a valuable tradeoff between complexity and overall system performance. Furthermore, RAS diversity is incorporated by using NBS and a new selection algorithm called HPG-PDBS to increase the channel capacity and enhance the error performance. Extensive analysis and simulations demonstrate the superiority of proposed scheme compared with conventional MU-MIMO. By using appropriate value of (η), it shows higher sum rate capacity and substantial increase in the user capacity up to two-fold at target BER and SNR values.

Distributed video coding (DVC) is a new video coding methodology that shifts the highly complex motion search components from the encoder to the decoder, such a video coder would have a great advantage in encoding speed and it is still able to achieve similar rate-distortion performance as the conventional coding solutions. Applications include wireless video sensor networks, mobile video cameras and wireless video surveillance, etc. Although many progresses have been made in DVC over the past ten years, there is still a gap in RD performance between conventional video coding solutions and DVC. The latest development of DVC is still far from standardization and practical use. The key problems remain in the areas such as accurate and efficient side information generation and refinement, quality control between Wyner-Ziv frames and key frames, correlation noise modelling and decoder complexity, etc. Under this context, this thesis proposes solutions to improve the state-of-the-art side information refinement schemes, enable consistent quality control over decoded frames during coding process and implement highly efficient DVC codec. This thesis investigates the impact of reference frames on side information generation and reveals that reference frames have the potential to be better side information than the extensively used interpolated frames. Based on this investigation, we also propose a motion range prediction (MRP) method to exploit reference frames and precisely guide the statistical motion learning process. Extensive simulation results show that choosing reference frames as SI performs competitively, and sometimes even better than interpolated frames. Furthermore, the proposed MRP method is shown to significantly reduce the decoding complexity without degrading any RD performance. To minimize the block artifacts and achieve consistent improvement in both subjective and objective quality of side information, we propose a novel side information synthesis framework working on pixel granularity. We synthesize the SI at pixel level to minimize the block artifacts and adaptively change the correlation noise model according to the new SI. Furthermore, we have fully implemented a state-of-the-art DVC decoder with the proposed framework using serial and parallel processing technologies to identify bottlenecks and areas to further reduce the decoding complexity, which is another major challenge for future practical DVC system deployments. The performance is evaluated based on the latest transform domain DVC codec and compared with different standard codecs. Extensive experimental results show substantial and consistent rate-distortion gains over standard video codecs and significant speedup over serial implementation. In order to bring the state-of-the-art DVC one step closer to practical use, we address the problem of distortion variation introduced by typical rate control algorithms, especially in a variable bit rate environment. Simulation results show that the proposed quality control algorithm is capable to meet user defined target distortion and maintain a rather small variation for sequence with slow motion and performs similar to fixed quantization for fast motion sequence at the cost of some RD performance. Finally, we propose the first implementation of a distributed video encoder on a Texas Instruments TMS320DM6437 digital signal processor. The WZ encoder is efficiently implemented, using rate adaptive low-density-parity-check accumulative (LDPCA) codes, exploiting the hardware features and optimization techniques to improve the overall performance. Implementation results show that the WZ encoder is able to encode at 134M instruction cycles per QCIF frame on a TMS320DM6437 DSP running at 700MHz. This results in encoder speed 29 times faster than non-optimized encoder implementation. We also implemented a highly efficient DVC decoder using both serial and parallel technology based on a PC-HPC (high performance cluster) architecture, where the encoder is running in a general purpose PC and the decoder is running in a multicore HPC. The experimental results show that the parallelized decoder can achieve about 10 times speedup under various bit-rates and GOP sizes compared to the serial implementation and significant RD gains with regards to the state-of-the-art DISCOVER codec.

The future of global telecommunications looks even more promising with the advent of Free Space Optics (FSO) to complement Fibre Optics technology. With the main impairments to Free Space Optics known to be diffraction and atmospheric turbulence, it is critical to adequately characterise the atmospheric medium for effective FSO system design. Most laser sources can be designed to produce Gaussian-like beam profiles, which suffer from diffraction issues. To address this, a non-diffracting beam called the Bessel beam is introduced; its central core has been proven to be resistant to diffractive spreading whilst propagating. However, both Gaussian and Bessel beams will experience distortion when propagating through atmospheric turbulence. The strength of atmospheric turbulence Cn2 is considered constant for ground-to-ground (terrestrial) applications, but proven variable and gradually-weakening for ground-to-space (satellite) applications. In this research, we investigate the propagation of the two beams both in the ground-to-ground scenario and in the ground-to-space scenario. For the ground-to-space scenario, we define a maximum height of 22 km above which the effect of atmospheric turbulence is considered negligible. We also investigate the propagation of the beams from the ground, beyond the 22 km limit, into deep space. We analyse and compare the performance of the beams for all the scenarios based on predefined performance measures. The Bessel beam offers enhanced performance and is shown to outperform the Gaussian on a number of the performance measures.

Este trabalho analisa as principais questões referentes à modernização do território brasileiro no início do século XX, a partir dos projetos idealizados por Francisco Bhering (1867-1924). Formado na Escola Politécnica do Rio de Janeiro, membro do Apostolado Positivista, professor das escolas politécnicas de São Paulo e do Rio de Janeiro e diretor da Repartição Geral dos Telégrafos, este engenheiro civil que completou seus estudos em Astronomia no Observatório de Paris atuou no sentido de promover o efetivo reconhecimento das áreas consideradas incógnitas do País. Para isto contou com o apoio de instituições como o Clube de Engenharia e a Sociedade de Geografia do Rio de Janeiro e de personalidades como o engenheiro militar Candido Rondon que tiveram efetiva participação na defesa da realização de seus dois grandes projetos a expansão da rede telegráfica até o Amazonas e a elaboração da Carta do Brasil ao milionésimo. Estes planos visavam atender à ânsia modernizadora do Estado republicano e das classes dominantes como parte do projeto de dominação e controle do território e de sua população. / This paper analyzes the main issues concerning of Brazil modernization in the early twentieth century, from the projects devised by Francisco Bhering (1867-1924). Formed at the Rio de Janeiro Polytechnic School, a member of the Positivist Apostolate, a professor of the São Paulo and Rio de Janeiro Polytechnic Schools and a Telegraph General Bureau director, the civil engineer who completed his studies in astronomy at the Paris Observatory acted to promote the effective recognition of the considered country \"unknown\" areas. That had the support of institutions like Engineering Club and Rio de Janeiro Geography Society and personalities as the military engineer Candido Rondon who have effective participation in the defense of his two major projects accomplish - the telegraph expansion to the Amazon and the Charter of Brazil to the millionth drafting. These plans were intended to satisfy the Republican State and master classes urge modernizing as part of the territory and its population domination and control project.