Performance and policy dimensions in internet routing

The Internet Routing Project, referred to in this report as the 'Highball Project', has been investigating architectures suitable for networks spanning large geographic areas and capable of very high data rates. The Highball network architecture is based on a high speed crossbar switch and an adaptive, distributed, TDMA scheduling algorithm. The scheduling algorithm controls the instantaneous configuration and swell time of the switch, one of which is attached to each node. In order to send a single burst or a multi-burst packet, a reservation request is sent to all nodes. The scheduling algorithm then configures the switches immediately prior to the arrival of each burst, so it can be relayed immediately without requiring local storage. Reservations and housekeeping information are sent using a special broadcast-spanning-tree schedule. Progress to date in the Highball Project includes the design and testing of a suite of scheduling algorithms, construction of software reservation/scheduling simulators, and construction of a strawman hardware and software implementation. A prototype switch controller and timestamp generator have been completed and are in test. Detailed documentation on the algorithms, protocols and experiments conducted are given in various reports and papers published. Abstracts of this literature are included in the bibliography at the end of this report, which serves as an extended executive summary

AMShare: Distributed Frequency Synchronization of Small Cell Base Transceiver Stations Utilizing Commercial AM Wireless Signals

Exponential growth of connected users in recent years and the increasing demands for ubiquitous coverage of wireless services has pushed the mobile operators to invest in innovative technologies that can support more connected users with higher quality of service. The idea of overlay network in cellular networks by adding small cells, has been proposed in recent years to improve network capacity and address the varying demands of mobile users in different areas. In deploying small cells as an overlay network, lots of technical challenges should be addressed. Stringent timing and synchronization requirements of the small cells are one of the challenges in implementing small cell radios. Currently, macro base transceiver stations use GNSS (Global Navigation Satellite Systems) receivers to comply with timing and synchronization requirements of the air interface standard (2G, 3G or LTE). However, the GNSS based synchronization solutions are not economically feasible in small cell implementations. Additionally, GNSS may not work well or at all in some indoor environments or in dense urban areas with high rise buildings where the canyon effect limits the sky view of the reviver. In this research, a new low cost frequency synchronization solution based on the commercial AM wireless signals is proposed. Each BTS in a small cell utilizes the carrier component embedded in a commercial AM wireless signal as the reference clock. Different small cell transceivers can then correct the relative CFO (Carrier Frequency Offset) between them using a common over the air reference clock. As part of the MW (Medium Wave) band, AM wireless signals can penetrate buildings and due to their ground-wave propagation have a relatively stable path that does not affect the transmitted signal. So they can be a good candidate for a synchronization solution. The proposed distributed frequency synchronization method is implemented using off the shelf components and its performance is evaluated in short term and long term measurement periods

NBS monograph

From Abstract: "This is a tutorial Monograph describing various aspects of time and frequency (T/F). Included are chapters relating to elemental concepts of precise time and frequency; basic principles of quartz oscillators and atomic frequency standards; historical review, recent progress, and current status of atomic frequency standards; promising areas for developing future primary frequency standards; relevance of frequency standards to other areas of metrology including a unified standard concept; statistics of T/F data analysis coupled with the theory and construction of the NBS atomic time scale; an overview of T/F dissemination techniques; and the standards of T/F in the USA. The Monograph addresses both the specialist in the field as well as those desiring basic information about time and frequency.

The determination and distribution of precise time

Methods for time determination including atomic clocks and distribution of timing signal

A Wireless Sensor Data Fusion Framework for Contaminant Detection

In the search for more effective instruments to collect data for the identification of threats to security, health, and safety, new tools must be designed to meet the challenges of a diverse set of possible applications. The extensive range of potential applications raises the need for a general purpose system capable of addressing a wide variety of deployment environments. This thesis focuses on a wireless sensor network framework for collecting environmental data in an effort to develop a sensing solution that fits within many design spaces. The framework includes reconfigurable wireless sensor node hardware, firmware, and software for interfacing sensor networks for upstream data aggregation and sensor data fusion. The wireless sensor modules utilize mesh network architecture to allow low power radios to be effective even with low sensor module dispersion density, or in environments that have obstructions which prevent line-of-sight communications. In the current implementation, the software is designed to allow a computer to be used to monitor all sensor module activities as data is collected, request information as needed, and forward collected data to a database system for further analysis. It also supports software modules to allow different sensor data fusion and analysis algorithms to be applied to the collected data in real-time

Proceedings of the Eleventh Annual Precise Time and Time Interval (PTTI) Application and Planning Meeting

Thirty eight papers are presented addressing various aspects of precise time and time interval applications. Areas discussed include: past accomplishments; state of the art systems; new and useful applications, procedures, and techniques; and fruitful directions for research efforts

Proceedings of the Fourth Precise Time and Time Interval Planning Meeting

The proceedings of a conference on Precise Time and Time Interval Planning are presented. The subjects discussed include the following: (1) satellite timing techniques, precision frequency sources, and very long baseline interferometry, (2) frequency stabilities and communications, and (3) very low frequency and ultrahigh frequency propagation and use. Emphasis is placed on the accuracy of time discrimination obtained with time measuring equipment and specific applications of time measurement to military operations and civilian research projects

Proceedings of the fifth annual NASA and Department of Defense Precise Time and Time Interval Planning Meeting

Subjects covered at this meeting were navigation, communications, applications of interferometry, frequency and time standards and synchronization, and radio wave propagation

Proceedings of the 8th Precise Time and Time Interval (PTTI) Applications and Planning Meeting

The Proceedings contain the papers presented at the Eight Annual Precise Time and Tme Interval PTTI Applications and Planning Meeting. The edited record of the discussions following the papers and the panel discussions are also included. This meeting provided a forum for the exchange of information on precise time and frequency technology among members of the scientific community and persons with program applications. The 282 registered attendees came from various U.S. Government agencies, private industry, universities and a number of foreign countries were represented. In this meeting, papers were presented that emphasized: (1) definitions and international regulations of precise time sources and users, (2) the scientific foundations of Hydrogen Maser standards, the current developments in this field and the application experience, and (3) how to measure the stability performance properties of precise standards. As in the previous meetings, update and new papers were presented on system applications with past, present and future requirements identified