Spacelab system analysis: A study of the Marshall Avionics System Testbed (MAST)

An analysis of the Marshall Avionics Systems Testbed (MAST) communications requirements is presented. The average offered load for typical nodes is estimated. Suitable local area networks are determined

Design and Performance Analysis of Functional Split in Virtualized Access Networks

abstract: Emerging modular cable network architectures distribute some cable headend functions to remote nodes that are located close to the broadcast cable links reaching the cable modems (CMs) in the subscriber homes and businesses. In the Remote- PHY (R-PHY) architecture, a Remote PHY Device (RPD) conducts the physical layer processing for the analog cable transmissions, while the headend runs the DOCSIS medium access control (MAC) for the upstream transmissions of the distributed CMs over the shared cable link. In contrast, in the Remote MACPHY (R-MACPHY) ar- chitecture, a Remote MACPHY Device (RMD) conducts both the physical and MAC layer processing. The dissertation objective is to conduct a comprehensive perfor- mance comparison of the R-PHY and R-MACPHY architectures. Also, development of analytical delay models for the polling-based MAC with Gated bandwidth alloca- tion of Poisson traffic in the R-PHY and R-MACPHY architectures and conducting extensive simulations to assess the accuracy of the analytical model and to evaluate the delay-throughput performance of the R-PHY and R-MACPHY architectures for a wide range of deployment and operating scenarios. Performance evaluations ex- tend to the use of Ethernet Passive Optical Network (EPON) as transport network between remote nodes and headend. The results show that for long CIN distances above 100 miles, the R-MACPHY architecture achieves significantly shorter mean up- stream packet delays than the R-PHY architecture, especially for bursty traffic. The extensive comparative R-PHY and R-MACPHY comparative evaluation can serve as a basis for the planning of modular broadcast cable based access networks.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Determining the feasibility of a method for improving bandwidth utilization of cable networks

While the cable television industry has made significant investments in infrastructure to improve the number and quality of services delivered to their end customers, they still face the problem of limited bandwidth of signals down the last mile of coaxial cable to the subscriber premises. This thesis investigates an approach devised by the author to overcome this limitation. The method involves clustering of channels in both the upstream and downstream directions in a DOCSIS compliant cable system. A model of this approach is made and the theoretical maximum throughput is calculated for several scenarios. Results are compared to performance of existing systems. It is found that proposed approach yields significantly more throughput for a given RF bandwidth than others in the comparison

Fiber Optics

Optical fibers in metrology, telecommunications, sensors, manufacturing, and health science have gained massive research interest. The number of applications is increasing at a fast pace. This book aims to present a collection of recent advances in fiber optics, addressing both fundamental and industrial applications. It covers the current progress and latest breakthroughs in emergent applications of fiber optics. The book includes five chapters on recent developments in optical fiber communications and fiber sensors, as well as the design, simulation, and fabrication of novel fiber concepts

ULTRA-WIDEBAND NONLINEAR ECHO-CANCELLATION

Hybrid fiber coaxial (HFC) networks are used around the world to distribute cable television and broadband internet services to customers. These networks are governed by the Data-Over-Cable Service Interface Specification (DOCSIS) family of standards, with the most recent version at the time of this writing being DOCSIS 3.1. A frequency division duplex (FDD) spectrum is used in DOCSIS 3.1, where the upstream and downstream signals are separated in frequency to eliminate interference. A possible method to increase signal bandwidths is to use a full-duplex (FDX) spectrum, in which the US and DS signals use the same frequencies at the same time. A main challenge faced when implementing FDX in a DOCSIS node is eliminating the interference in the received US signal caused by the transmitted DS signal. One possible method for eliminating the interference is utilizing an echo-canceling algorithm, which predicts the self-interference (SI) based on the known DS signal and cancels it from the received US signal. Although echo-cancellation algorithms exist for fundamentally similar applications, the DOCSIS FDX case is more complicated for two main reasons. First, the DOCSIS node uses a nonlinear power amplifier to amplify the DS signal. Second, the DS signal is an ultra-wideband signal spanning a frequency range of up to 1.2 GHz. Most of the amplifier modeling techniques discussed in the literature were designed for narrowband wireless signals and will have limited performance when used with ultra-wideband signals. This thesis develops an algorithm to characterize the power amplifier and to predict the harmonics it generates for a given DS signal. These predicted harmonics can be used to cancel the SI signal in a full duplex DOCSIS system. The algorithm, which is referred to as the ultra-wideband memory polynomial (UWB-MP) model, is based on the well-known memory polynomial model with adaptations which allow the model to predict harmonics for ultra-wideband signals. Since a direct implementation of the UWB-MP model in an FPGA would result in very high resource usage, system architecture recommendations are provided. Our proposed implementation of the model compensates for harmonics up to and including the 3rd order, which has a power spectrum extending above 3600 MHz. Using the techniques discussed in this thesis, it is shown that a sampling rate of 4 GHz allows for cancellation of the SI signal while providing a reasonable balance between performance and resource usage. Matlab simulations of a DOCSIS node with various parameters and PA simulation models were conducted. The simulations showed that over 75 dB of cancellation of the SI signal is possible in an idealized hardware setup. It is also demonstrated that AWGN injected into the received signal does not reduce the ability of the model to estimate the PA harmonics, although the noise itself cannot be canceled. Further simulations showed that the UWB-MP model could cancel harmonics whose power is much higher than that specified in DOCSIS. Although the UWB-MP model was designed with memory polynomial type PAs in mind, simulation results show that significant cancellation is possible with PAs that are represented by Wiener models as well. Based on the simulation results, we recommend using a filter of length 20 coefficients for each harmonic in the UWB-MP model, and 60 iterations with 500 samples for estimating the coefficients with the least squares method

Data transmissions through HFC return channels

Master'sMASTER OF ENGINEERIN