Design and Development of a Robust, Reliable Remote Input Device for Virtual Reality Environments

Visualization is the most important and helpful part of any scientific research activity. Almost all of the research and development requires specific and in some cases real-time visualization of the simulation. HLRS visualization department support scientists and engineers with visual analysis of the simulated data computed by high performance computers. With time the complexity and size of the simulated data set is increasing and in order to keep up with the technology, new and state of the art techniques are being utilized for data visualization. Currently the visualization department is working on a 3D virtual reality environment called CAVE which allows to simulate data sets intuitively. This virtual reality environment need some kind of control and navigation capability form humans and for this purpose a prototype of a remote device is being developed. This remote device is used to control and navigate scenes and simulation models within the virtual reality environment of CAVE. The first prototype of this remote device consists of AVR atmega micro-controller and a RF module operating at 2.4 GHz. The same set of devices is present on the receiver side as an AVR controller and a RF module which is then connected to the CAVE via USB. The main objective of this thesis work is to implement a reliable, robust and low-latency bi-directional communication protocol between multiple remote devices and a receiver device inside CAVE. Also improve the power efficiency of the remote device regarding run-time and stand-by time, redesign the remote device to support the target application with feedback to the user. In order to improve the reliability first the reliability is defined regarding our environment requirements, then various key factors which reduce the reliability are studied and their solutions are implemented and finally the implementation is evaluated. The latency will remain a key point in all of the implementations regarding robustness and reliability of wireless link. The communication protocol will be extended to handle multiple remote devices with bi-directional capability with one receiver. The goal of making the remote device maximum power efficient is investigated by exploiting the different operating modes of the RF module during the run-time and stand-by time of the remote device. Latency will remain a trade-off with power efficiency and reliability

On Short Forward Error-Correcting Codes for Wireless Communication Systems

Abstract—For real-time wireless communications, short forward error-correcting (FEC) codes are indispensable due to the strict delay requirement. In this paper we study the performance of short FEC codes. Reed-Solomon (RS) codes and concatenated zigzag (CZ) codes are chosen as representatives of classical algebraic codes and modern simple iterative decodable codes, respectively. Additionally, we use random binary linear codes as a baseline reference for comparison. Our main results (demonstrated by both simulation and ensemble distance spectrum analysis) are as follows: 1) Short RS codes are as good as random binary linear codes; 2) Carefully designed short lowdensity parity-check (LDPC) codes are almost as good as random binary linear codes when high decoding complexity can be tolerated; 3) Low complexity belief propagation decoders incur considerable performance loss at short coding lengths. Keywords-Reed-Solomon (RS) codes;low-density parity-check (LDPC) codes; Adaptive belief-propagation (ABP) I

Quality of service for VoIP in wireless communications

Ever since telephone services were available to the public, technologies have evolved to more efficient methods of handling phone calls. Originally circuit switched networks were a breakthrough for voice services, but today most technologies have adopted packet switched networks, improving efficiency at a cost of Quality of Service (QoS). A good example of packet switched network is the Internet, a resource created to handle data over an Internet Protocol (IP) that can handle voice services, known as the Voice over the Internet Protocol (VoIP). The combination of wireless networks and free VoIP services is very popular, however its limitations in security and network overload are still a handicap for most practical applications. This thesis investigates network performance under VoIP sessions. The aim is to compare the performance of a variety of audio codecs that diminishes the impact of VoIP in the network. Therefore the contribution of this research is twofold: To study and analyse the extension of speech quality predictors by a new speech quality model to accurately estimate whether the network can handle a VoIP session or not and to implement a new application of network coding for VoIP to increase throughput. The analysis and study of speech quality predictors is based on the mathematical model developed by the E-model. A case study of an embedded Session Initiation Protocol (SIP) proxy, merged with a Media Gateway that bridges mobile networks to wired networks has been developed to understand its effects on QoS. Experimental speech quality measurements under wired and wireless scenarios were compared with the mathematical speech predictor resulting in an extended mathematical solution of the E-model. A new speech quality model for cascaded networks was designed and implemented out of this research. Provided that each channel is modelled by a Markov Chain packet loss model the methodology can predict expected speech quality and inform the QoS manager to take action. From a data rate perspective a VoIP session has a very specific characteristic; exchanged data between two end nodes is often symmetrical. This opens up a new opportunity for centralised VoIP sessions where network coding techniques can be applied to increase throughput performance at the channel. An application layer has been implemented based on network coding, fully compatible with existing protocols and successfully achieves the network capacity.EThOS - Electronic Theses Online ServiceGBUnited Kingdo