Browsing by Subject "Relay"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Modeling the pneumatic relay valve of an s-cam air brake(Texas A&M University, 2005-08-29) Vilayannur Natarajan, ShankarStatistics indicate that defects in brake system contribute significantly to fatal crashes involving commercial vehicles. Hence there is a need for developing preventive and active safety measures for assessing the performance of an air brake system in trucks. Existing techniques for assessing the performance of brakes are infrastructure intensive, time and labor intensive. The premise of this thesis is that model-based diagnostic techniques can be employed to overcome these limitations of existing tech- niques. The design of a model-based diagnostic system requires the development and experimental corroboration of a mathematical model of the evolution of pressure in each brake chamber of a truck in response to the application of brake pedal input by the driver, when there are no faults or defects in the brake system. This thesis is aimed at modeling and experimentally corroborating a subsystem of an air brake system, namely the pneumatic relay valve. The pneumatic relay valve takes a input signal from the primary delivery of a treadle valve and meters air from a storage reservoir to Type 30 rear brake chambers. A description of the development of the model, the experimental setup and corroborating experimental results are provided.Item Relay-aided communications with partial channel state information(2011-08) Yazdan Panah, Ali; Heath, Robert W., Ph. D.; Evans, Brian L.; Hasenbein, John; Vikalo, Haris; Andrews, Jeffrey G.Modern wireless communication systems strive to enable communications at high data rates, over wide geographical areas, and to multiple users. Unfortunately, this can be a daunting task in practice, as natural laws governing the wireless medium may hinder point-to-point transmissions. Communications over large distances (path loss), and physical obstructions in line-of-sight signals (shadowing) are prime examples of such impediments. One promising solution is to deploy intermediary terminals to help reestablish such broken point-to-point communication links. Such terminals are called relay nodes, and the corresponding systems are referred to as being relay-aided. As in the case of point-to-point communication, design of efficient transmission and reception techniques in relay-aided systems depends on the availability of propagational channel state information. In practice, such information is only accurate to a certain degree which is governed by overhead constraints, feedback delay, and channel fluctuations due to mobility. Understanding the impacts of such partial channel state information, and devising transmission and reception methods based on such understandings, is the main topic of this dissertation. The transmission protocol classifies relays as either one-way, where the relay receives signals from one terminal, or two-way, where the relay receives signals from more than one terminal. Designs and solutions for both one- and two-way relaying systems are presented in this dissertation. Emphasis is placed on two-way relaying systems given their superior efficiency in utilizing channel resources. For one-way relaying this dissertation presents power loading strategies for multiuser-multicast systems derived based on the availability of full or partial channel state information at the terminals. In the case of two-way relaying, both single and multi-user systems are analyzed. For single-user two-way relaying, this dissertation presents optimal methods of acquiring partial channel state information via pilot-aided channel estimation methods. This includes an analysis of the effects of channel estimation upon the system sum-rate. Also, the design of channel equalizers exhibiting robustness to partial channel state information is proposed. For multi-user two-way relaying, this dissertation presents several precoding strategies at the relay terminal(s) to combat the effects co-channel interference in light of the existence of self-interference inherent to two-way relaying operations.