The objective of this research is to comprehensively compare bulk accumulation and inversion MOSFETs, and find application areas where each is superior.Short channel effect (SCE) models for accumulation and inversion MOSFETs are derived that accurately predict threshold voltage, subthreshold swing, and subthreshold current. A source/drain junction depth dependent characteristic length is derived that can be used to rapidly assess the impact of junction depth scaling on minimum channel length. A fast circuit simulation methodology is developed that uses physically based I-V models to simulate inversion and accumulation MOSFET inverter chains, and is found to be accurate over a wide range of supply voltages. The simulation methodology can be used for rapid technology optimization, and performance prediction. Design guidelines are proposed for accumulation MOSFET design; the guidelines result in a low process sensitivity, low SCE, and a subthreshold current less than the allowable limit. The relative performance advantage of accumulation/inversion MOSFETs is gate-technology dependent. In critical comparisons, on-current is evaluated by means of a full band Monte Carlo device simulation. Gate-leakage, and band-to-band tunneling leakage at the drain-substrate region are included in the performance analysis. For mid-bandgap metal gate, accumulation MOSFETs perform better than inversion MOSFETs for hi-performance (HiP) and low-operating power (LOP) applications. For tunable metal gate technology, inversion MOSFETs always perform better than accumulation MOSFETs. For dual poly technology, accumulation MOSFETs perform better than inversion MOSFETs for low standby power (LSTP) applications. A comprehensive scaling analysis has been performed on accumulation and inversion MOSFETs using both SCE models and 2-D simulations. Results show that accumulation MOSFETs can scale better than inversion MOSFETs for mid-bandgap metal gate HiP, and LOP applications; and poly gate LSTP applications.

In this thesis, we study channel estimation in time-varying cooperative network. Since channels vary with time, we insert training blocks periodically to trace channel variation. In this work, we adopt Kalman filter to trace channel variation due to its low complexity. By storing previous channel estimate, Kalman filter simply requires to process next received vectors to update current channel estimate. We use all past observations to estimate current channel state to avoid wasting information. In content of cooperation, we directly estimate effective channel from source through relay to the destination. The reason is that, we separately estimate the source-relay and relay-destination links, relays need extra efforts to estimate the channel and feedback estimates to the destination. It will increase the computational loading on relays, and the feedback channel may suffer channel fading, resulting in more distortion of estimates. Therefore, the destination directly estimate effective channel, using Kalman filter to trace variation. Furthermore, we design pre-coding scheme on relays for forwarding training symbols in order to reduce channel estimation errors and obtain more accurate channel information. To detect data symbols, we need to channel state information over each data block as well. Therefore, estimates over previous training blocks are interpolated to estimate channel over data blocks based on LMMSE criterion. Since estimates over training blocks are obtained from Kalman filter, it consequently improves estimation quality of the channel over the data blocks. The main contributions of the thesis are optimal training design to reduce the estimation error, the estimation based on Kalman filter, and linearly combing the estimates to provide more accurate estimates of the channels over data blocks.

In this thesis heterogeneous bipolar plates are applied to pure hydrogen PEMFC (called HFC) stacks. The experimental methods are adopted to study the performance and characteristics of the cell under certain operational conditions. In order to obtain the permeability of carbon fiber bipolar plates the pressure drops and flow rates are measured on the two sides of the carbon fiber bunch. A test device has been developed to separate the gas of the two sides so that the gas can only flow through the gaps between carbon fibers. Additionally, the gas pressures on the flow channel and the output voltage of each cell in several locations are measured to help us to understand their relationships. The flow characteristics of the gas reactants in these carbon fiber bipolar plates can also be understood from these measurements. A bipolar plate with the parallel or serpentine flow channel can be formed by properly arranging the carbon fiber bunches. However, if the oxidizer is air and only single inlet and outlet in cathode chamber are designed, the oxidizer can always not be supplied sufficiently in high power density. The experimental studies display that the output voltages of cells in the midstream or downstream are far below the output voltage in the upstream. The voltage of cells in the upstream is the highest, the next one is in the downstream, and the lowest one is located in the midstream due to accumulating of nitrogen. The insufficiency of oxidizer occurs more seriously in the parallel flow channel than that in serpentine flow channel in single inlet and outlet design. The distribution of current is not uniform especially near midstream, although this phenomenon can be improved by increasing the air inlet pressure. However, the problems are hard to solve in large MEA if we just increase the inlet pressure. Another strategy is needed to solve this problem. In order to solve the insufficient supply of air in single inlet and outlet design, multiple inlets and outlets are designed. In this design multiple entries can supply enough fresh air driven by fan, and multiple exits can exhaust inert gas by exhausting fan to avoid accumulating in a reactive chamber so that the performance of stack can be improved dramatically.

Pico-Cellular architecture fully reuses frequency to increase network capacity. However, it will increase the occurance of Handoff due to the small range of cell. Previous works in channel allocations can reduce blocking probability of handoff call, but it may increase blocking probability of new call. As a result, channel utilization is decreased because they can not adapt to network changes. In this thesis, we present a Dynamic Channel Allocation Mechanism with priority support. All channels and calls are divided into high and low priority. If there is no high_priority channel for high_priority call, high_priority call may downgrade its priority by sacrificing some QoS to utilize low_priority channels. We define two new array for network information status, one is next_cell state, and the other is the transition probability. Next_cell state is used to save prior M Cell_Ids where handoff calls may move to. Transition probability is used to save the probabilities for active calls moving to other neighboring cells. According to next_cell state and transition probability, we can accurately predict the probabilities for mobile hosts moving to other neighboring cells. Therefore, we can dynamically adjust bandwidth reservation requests sending to neighboring cells by the latest transition probability and the number of active calls in this cell. We analyze the proposed mechanism through a mathematical model. In the model, we build a four-dimension Markov Chain and use MATLAB[41] tool to evaluate blocking probability, channel throughput and utilization. We found out that blocking probability of handoff call can be decreased and channel utilization can be increased through the proposed channel allocation mechanisms with high and low priority support.

Abstract Slope to Basin-floor Evolution of Channels to Lobes, Jurassic Los Molles Formation, Neuquén Basin, Argentina Nataleigh Kristine Vann, MS Geo Sci The University of Texas at Austin, 2013 Supervisor: Ronald J. Steel and Cornel Olariu The relatively steep and short-headed Neuquén Basin margin provides an excellent laboratory for demonstrating down slope changes in sediment gravity flow bed thickness, grain size and facies, as well as channel to lobe transitions. Approximately 400m high clinoformal, shelf-slope-basin-floor deposits of Jurassic Los Molles Formation outcrops are evaluated for reservoir scale definition of facies and architectures in the La Jardinera field area, Neuquén Basin. Slope deposits represent the accretionary front of the prograding shelf margin that were fed by a coarse grained shelf (Lajas Formation). Mapping of a high-resolution satellite images draped on digital elevation model resolved a sub-meter stratigraphic framework. Thirty-three measured sections from outcrops exposed along a 5km transect characterize the evolution of sand body architectures from the shelf edge to the basin floor. The Neuquén Basin margin is typified by four main depositional environments that transition from shelf edge incisions filled with conglomerates, to confined channels in upper- to middle-slope reaches, to weakly confined channels on the lower slope to sheet-like lobes and distributary channel complexes that drape onto both the lower slope and basin floor. Along the slope to basin floor profile the depositional architecture changes by overall decrease in grain size, amalgamation of beds and degree of erosion. Confined slope channels are up to 25m deep, isolated within muddy slope deposits and have complex multistory fills marked by basal and internal erosive contacts lined with mud-clast and/or pebble conglomerates. Channel axes contain amalgamated, medium to coarse sandstones that thin and fine towards channel margins over 100m. Down dip, lower slope channels are up to 400m wide and less than 10m thick. A marked reduction in mud clasts and conglomeratic material at basal erosional surfaces in weakly confined channels represent a downslope decrease in flow energy. However, distinct meter scale erosion surfaces continue to be recognizable where thin ripple laminated sands are truncated on channel margins by amalgamated structureless sands. Erosional surfaces are absent in laterally extensive (>5km), sheet-like lobes of basin-floor fans that are generally finer grained than lower or upper slope channel fills. There are lenticular debrites and thin micro-conglomerates associated with basin-floor fans. / text

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / The goal of this paper is to implement a model of multipath fading in a radio channel simulator for aeronautical applications. When developing a wireless communications system, it is useful to perform simulations of the radio context in which the system has to operate. A radio link is substantially composed by three parts: transmitting segment, transmission channel and receiving segment. We focus our attention on the radio channel propagation. We proposed two geometrical models of a territory corresponding to a determined flight area and, after importing the data needed to estimate our parameters, we compared our results with the channel soundings in literature, obtaining comparable values.

This paper presents the investigations into the performance of a multiple-input multiple-output (MIMO) system with its transmitters on a spinning vehicle and no available channel state information (CSI) at the transmitter or the receiver. The linear least squares approach is used to estimate the channel and the estimation error is measured. Spinning gives rise to a periodic component in the channel which can be estimated based on the spin rate relative to the data rate of the system. It is also determined that spinning causes the bit error rate of the system to degrade by a few dB.

The intricate dependency of networking protocols upon the performance of the wireless channel motivates the investigation of network channel approximations for fading channels. Wireless networking protocols are increasingly being designed and evaluated with the assistance of networking simulators. While evaluating networking protocols such as medium access control, routing, and reliable transport, the network channel model, and its associated capacity, will drastically impact the achievable network throughput. Researcher relying upon simulation results must therefore use extreme caution to ensure the use of similar channel models when performing protocol comparisons. Some channel approximations have been created to mimic the behavior of a fading environment, however there exists little to no justification for these channel approximations. This dissertation addresses the need for a computationally efficient fading channel approximation for use in network simulations. A rigorous flat fading channel model was developed for use in accuracy measurements of channel approximations. The popular two-state Markov model channel approximation is analyzed and shown to perform poorly for low to moderate signal-to-noise ratios (SNR). Three novel channel approximations are derived, with multiple methods of parameter estimation. Each model is analyzed for both statistical performance and network performance. The final model is shown to achieve very accurate network throughput performance by achieving a very close matching of the frame run distributions. This work provides a rigorous evaluation of the popular two-state Markov model, and three novel low complexity channel models in both statistical accuracy and network throughput performance. The novel models are formed through attempts to match key statistical parameters of frame error run and good frame run statistics. It is shown that only matching key parameters is insufficient to achieve an acceptable channel approximation and that it is necessary to approximate the distribution of frame error duration and good frame run duration. The final novel channel approximation, the three-state run-length model, is shown to achieve a good approximation of the desired distributions when some key statistical parameters are matched.

Joint source-channel coding (JSCC) has emerged to be a major field of research recently. Channel optimized vector quantization (COVQ) is a simple feasible JSCC scheme introduced for communication over practical channels. In this work, we propose an iterative design algorithm, referred to as the iterative maximum a posteriori (MAP) decoded (IMD) algorithm, to improve COVQ systems. Based on this algorithm, we design a COVQ based on symbol MAP hard-decision demodulation that exploits the non-uniformity of the quantization indices probability distribution. The IMD design algorithm consists of a loop which starts by designing a COVQ, obtaining the index source distribution, updating the discrete memoryless channel (DMC) according to the achieved index distribution, and redesigning the COVQ. This loop stops when the point-to-point distortion is minimized. We consider memoryless Gaussian and Gauss-Markov sources transmitted over binary phase-shift keying modulated additive white Gaussian noise (AWGN) and Rayleigh fading channels. Our scheme, which is shown to have less encoding complexity than conventional COVQ and less encoding complexity and storage requirements than soft-decision demodulated (SDD) COVQ systems, is also shown to provide a notable signal-to-distortion ratio (SDR) gain over the conventional COVQ designed for hard-decision demodulated channels while sometimes matching or exceeding the SDD COVQ performance, especially for higher quantization dimensions and/or rates. In addition to our main result, we also propose another iterative algorithm to design SDD COVQ based on the notion of the JSCC error exponent. This system is shown to have some gain over classical SDD COVQ both in terms of the SDR and the exponent itself. / Thesis (Master, Mathematics & Statistics) -- Queen's University, 2008-08-29 17:58:52.329

This thesis is concerned with the channel assignment (CA) problem in multi-channel multi-interface wireless mesh networks (M2WNs). First, for M2WNs with general topologies, we rigorously demonstrate using the combinatorial principle of inclusion/exclusion that the CA solution space can be quantified, indicating that its cardinality is greatly influenced by the number of radio interfaces installed on each router. Based on this analysis, a novel scheme is developed to construct a new reduced search space, represented by a lattice structure, that is searched more efficiently for a CA solution. The elements in the reduced lattice-based space, labeled Solution Structures (SS), represent groupings of feasible CA solutions satisfying the radio constraints at each node. Two algorithms are presented for searching the lattice structure. The first is a greedy algorithm that finds a good SS in polynomial time, while the second provides a user-controlled depthfirst search for the optimal SS. The obtained SS is used to construct an unconstrained weighted graph coloring problem which is then solved to satisfy the soft interference constraints. For the special class of full M2WNs (fM2WNs), we show that an optimal CA solution can only be achieved with a certain number of channels; we denote this number as the characteristic channel number and derive upper and lower bounds for that number as a function of the number of radios per router. Furthermore, exact values for the required channels for minimum interference are obtained when certain relations between the number of routers and the radio interfaces in a given fM2WN are satisfied. These bounds are then employed to develop closed-form expressions for the minimum channel interference that achieves the maximum throughput for uniform traffic on all communication links. Accordingly, a polynomial-time algorithm to find a near-optimal solution for the channel assignment problem in fM2WN is developed. Experimental results confirm the obtained theoretical results and demonstrate the performance of the proposed schemes.