Don Gruenbacher

The great plains environment for network innovation (GpENI):a programmable testbed for future internet architecture research

The Great Plains Environment for Network Innovation – GpENI is an international programmable network testbed centered on a regional optical network in the Midwest US, providing flexible infrastructure across the entire protocol stack. The goal of GpENI is to build a collaborative research infrastructure enabling the community to conduct experiments in future Internet architecture. GpENI is funded in part by the US National Science Foundation GENI (Global Environments for Network Innovation) program and by the EU FIRE (Future Internet Research and Experimentation) Programme, and is affiliated with a project funded by the NSF FIND (Future Internet Design) Program.

Epidemic spreading on weighted contact networks

The study of epidemics is a crucial issue to several areas. An epidemic can have devastating economic and social consequences. A single crop disease in Kansas could destroy the yearly income of many farmers. Previous work using graph theory has determined a universal epidemic threshold found in the graph topology for a binary contact network in the compartmental susceptible-infected (SI) analysis. We expand this threshold to a more realistic measure. A binary uniform level of contact within a society is too idealistic and an improved threshold is found in allowing a spectrum of contact within a contact network. The expanded contact network also allows for asymmetric contact such as a mother caring for her child. Further study in this area should lead to improved simulators, disease modeling, policies and control of infectious diseases and viruses.

A simple algorithm for generating discrete prolate spheroidal sequences

The discrete prolate spheroidal sequences are optimum waveforms in many communication and signal processing applications because they comprise the most spectral efficient set of orthogonal sequences possible. Generation of the sequences has proven to be difficult in the past due to the absence of a closed form solution. A new method of easily generating any single discrete prolate spheroidal sequence, including sequences of very long length, is presented. Also shown are some example sequences generated using the algorithm presented. >

Using GENI for experimental evaluation of Software Defined Networking in smart grids

Abstract The North American Electric Reliability Corporation (NERC) envisions a smart grid that aggressively explores advance communication network solutions to facilitate real-time monitoring and dynamic control of the bulk electric power system. At the distribution level, the smart grid integrates renewable generation and energy storage mechanisms to improve the reliability of the grid. Furthermore, dynamic pricing and demand management provide customers an avenue to interact with the power system to determine the electricity usage that best satisfies their lifestyle. At the transmission level, efficient communication and a highly automated architecture provide visibility in the power system and as a result, faults are mitigated faster than they can propagate. However, such higher levels of reliability and efficiency rest on the supporting communication infrastructure. To date, utility companies are moving towards Multiprotocol Label Switching (MPLS) because it supports traffic engineering and virtual private networks (VPNs). Furthermore, it provides Quality of Service (QoS) guarantees and fail-over mechanisms in addition to meeting the requirement of non-routability as stipulated by NERC. However, these benefits come at a cost for the infrastructure that supports the full MPLS specification. With this realization and given a two week implementation and deployment window in GENI, we explore the modularity and flexibility provided by the low cost OpenFlow Software Defined Networking (SDN) solution. In particular, we use OpenFlow to provide (1) automatic fail-over mechanisms, (2) a load balancing, and (3) Quality of Service guarantees: all essential mechanisms for smart grid networks.

Implementation of a Flexible Encoder for Structured Low-Density Parity-Check Codes

The hardware implementation of an encoder for randomly generated low-density parity-check (LDPC) codes requires large area. Using structured LDPC codes decreases the encoding complexity and also provides design flexibility. In this paper, an architecture for implementing an encoder is presented that adheres to the structured LDPC codes defined in the IEEE 802.16e standard. The design methodology is flexible in terms of both the code rate and code length. Results are provided for an implementation on a Stratix FPGA for codes with rates 1/2, 2/3, 3/4 and 5/6, and block lengths ranging from 576-2304. The number of logic elements, clock speed, and throughput of the encoder for the different code lengths are presented. The design achieves encoding rates in excess of 400 Mbps.

A Maximum Power Tracking Technique for Grid-Connected DFIG-Based Wind Turbines

In this paper, a maximum power tracking technique is presented for doubly fed induction generator-based wind turbines. The presented technique is a novel version of the conventional method, i.e., the electrical torque is proportional to the square of the rotor speed, in which the proportional coefficient is adaptively adjusted in real-time through three control laws. The first control law calculates the desired electrical torque using feedback linearization, assuming that the power capture coefficient and the desired rotor speed are instantaneously identified. The second control law estimates the real-time values of the power capture coefficient from a Lyapunov-based analysis, and the third control law provides the desired rotor speed. These control laws cause the turbine to adaptively adjust the rotor speed toward a desired speed in which the operating point moves in the direction of increasing the power capture coefficient. The proposed maximum power tracking method differs distinctly from the perturb-and-observe scheme by eliminating a need for adding a dither or perturbation signal, and robustly tracks the trajectory of maximum power points even in the event of a sudden wind speed change that can cause the perturb-and-observe technique to fail. In this paper, the National Renewal Energy Laboratory 5-MW reference wind turbine model is used to demonstrate the validity and robustness of the proposed method.

Performance of coded OFDM in a fading environment using high rate low-density parity-check codes

A bit error analysis of wideband OFDM systems that use high rate (0.67/spl les/R/spl les/0.95) low-density parity-check codes for bit-error protection is presented. Subcarrier modulation methods of BPSK, QPSK, and 16-QAM are implemented on channel models that include shadowed Rician fading and additive white Gaussian noise. The performance of different low-density parity check (LDPC) codes constructed through random and systematic methods is also compared.

Design and verification techniques used in a graduate level VHDL course

The use of the VHSIC Hardware Description Language (VHDL) has become very important to the simulation and implementation of digital systems in both industry and educational settings. Although VHDL is a powerful language with many capabilities, it has downfalls when considering the difficulty in learning the language as well as its limited capabilities for transitioning a design from initial concept to design entry and verification stages. This paper discusses techniques used to teach the VHDL design methodology to graduate students, as well as methods used to go through a complete design cycle from initial concept to final implementation. VHDL design techniques were developed using various projects and homework assignments, and different approaches to implementing the same function allowed direct comparisons of the speed and size of the designs. Different processes for taking a design from initial concept through chip implementation were discussed, and one example of the process is discussed here. A Finite Impulse Response (FIR) filter was conceptually designed using the MATLAB programming environment to determine adequate performance specifications such as filter size and quantization levels. The design was then written using a behavioral VHDL coding style, as well as a VHDL test bench to determine if the VHDL behavioral model provided the same results as the MATLAB model. After design synthesis of the behavioral description using Synopys tools, the same test bench was used again to verify the performance of the structural VHDL netlist with annotated place and route delay information provided from the Alters MaxPluslI tools. Final verification took place with at the board level using an Altera CPLD programmed with the FIR filter design.

Simulative Comparison of Multiprotocol Label Switching and OpenFlow Network Technologies for Transmission Operations

Utility companies are integrating multiprotocol label switching (MPLS) technologies into existing backbone networks, including networks between substations and control centers. MPLS has mechanisms for efficient overlay technologies as well as mechanisms to enhance security: features essential to the functioning of the smart grid. However, with MPLS routing and other switching technologies innovation is restricted to the features enclosed “in the box.” More specifically, there is no practical way for utility operators or researchers to test new ideas such as alternatives to IP or MPLS on a realistic scale to obtain the experience and confidence necessary for real world deployments. As a result, novel ideas go untested. Conversely, the OpenFlow framework has enabled significant advancements in network research. OpenFlow provides utility operators and researchers the programmability and flexibility necessary to enable innovation in next-generation communication architectures for the smart grid. This level of flexibility allows OpenFlow to provide all features of MPLS and also allows OpenFlow devices to co-exist with existing MPLS devices. The simulation results in this paper demonstrate that OpenFlow performs as well as MPLS, and may therefore be considered an alternative to MPLS for smart grid applications.

Performance of spread OFDM with LDPC coding in outdoor environments

The performance of OFDM systems that utilize coding and spreading is presented. The proposed systems operate in outdoor environments and achieve coding gains through the use of low-density parity-check (LDPC) encoding. It is shown that by introducing Hadamard-Walsh spreading in coded OFDM, additional gain in performance can be attained relative to uncoded as well as LDPC coded OFDM systems. Comparable systems using convolutional codes are shown to have similar performance, although the OFDM system require additional interleaving and deinterleaving.