Randall Nealy

Compact antennas for UWB applications

This paper reports on an investigation of spherical, disc, and half-disc antennas in the frequency and time domains with the objective of developing small planar versions of the antennas. These antennas have an omni-directional impulse response in azimuth and a pulse duration of 0.5 - 0.65 nanoseconds. In addition, the measured data show a reasonable peak received signal in a pulse communication link using two identical antennas.A report on an investigation of spherical, disc, and half-disc antennas in the frequency and time domains with the objective of developing small planar versions of the antennas. These antennas have an omni-directional impulse response in azimuth and pulse duration of 0.5-0.65 nanoseconds. In addition, the measured data show a reasonable peak received signal in a pulse communication link using two identical antennas.

On the Co-Existence of TD-LTE and Radar Over 3.5 GHz Band: An Experimental Study

This letter presents a pioneering study based on a series of experiments on the operation of commercial Time-Division Long-Term Evolution (TD-LTE) systems in the presence of pulsed interfering signals in the 3550-3650 MHz band. TD-LTE operations were carried out in channels overlapping and adjacent to the high power SPN-43 radar with various frequency offsets between the two systems to evaluate the susceptibility of LTE to a high power interfering signal. Our results demonstrate that LTE communication using low antenna heights was not adversely affected by the pulsed interfering signal operating on adjacent frequencies irrespective of the distance of interfering transmitter. Performance was degraded only for very close distances (1-2 km) of overlapping frequencies of interfering transmitter.

Wideband RF front end design considerations for a flexible white space software defined radio

This paper introduces a flexible RF front end for whitespace communication. The designed front end can operate over any frequency from 100 MHz to 2.5 GHz and the channel bandwidth can be programmable from 4.5 kHz to 10 MHz. This large frequency range and wide bandwidth makes this hardware suitable for implementing most wireless standards. A direct conversion RFIC developed by Motorola, drives the core of the RF front end. The various RF parameters can be changed by programming this RFIC through a serial peripheral interface (SPI). As part of this work we further develop an intelligent software driver to control different parameters of the RFIC. Thus the combination of highly flexible front end and flexible software driver makes this hardware an excellent choice for whitespace devices. The performance of this front end has been tested and measured and has been integrated into a daughterboard format for the Universal Software Radio Peripheral (USRP), a hardware device which enables the rapid design and implementation of software defined radio (SDR).

Software-Defined LTE Evolution Testbed Enabling Rapid Prototyping and Controlled Experimentation

The long-term evolution (LTE) has spread around the globe for deploying 4G cellular networks for commercial use. These days, it is gaining interest for new applications where mobile broadband services can be of benefit to society. Whereas the basic concepts of LTE are well understood, its long-term evolution has just started. New areas of Ramp;amp;D look into operation in unlicensed and shared bands, where new versions of LTE need to coexist with other communication systems and radars. Virginia Tech has developed an LTE testbed with unique features to spur LTE research and education. This pa-per introduces Virginia Techs LTE testbed, its main features and components, access and configuration mechanisms, and some of the research thrusts that it enables. It is unique in several aspects, including the extensive use of software-defined radio technology, the combination of industry-grade hardware and software-based systems, and the remote access feature for user- defined configurations of experiments and radio frequency paths.

Analysis of directional antenna for railroad crossing safety applications

A rapidly deployable and cost-effective railroad crossing early warning system integrated with the railway system is attractive due to its protection of the unmanned grade crossings, which requires a warning system with long-distance communication link. In this paper, we investigate the problem of suitable antenna selection for such a railway warning system First, the antenna criteria for railroad crossing safety applications are described based on practical system considerations, the safe distances on the road and on the railway. Then, the optimal antenna pattern is derived theoretically to get the smallest size which fits for the practical installation. We also conducted a feasibility study of an array antenna through measurements on a near field scanner.

Measurement and Configuration of DSRC Radios for Vehicle-to-Train (V2T) Safety-Critical Communications

Despite the rapid development of wireless technology, there has been little application of the technology to improve railroad crossing safety. We present vehicle-to-railroad channel characterization and dedicated short range communications (DSRC) performance results at railroad crossings in rural and suburban environments. Our results show that an omnidirectional antenna provides slightly better performance in rural conditions. However, a bi-directional antenna increased warning range by more than 200 m in suburban conditions. A proper configuration of the DSRC radio provides reliable warning of an approaching train for cars near a railroad crossing.

LTE Spectrum Sharing Research Testbed: Integrated Hardware, Software, Network and Data

This paper presents Virginia Techs wireless testbed supporting research on long-term evolution (LTE) signaling and radio frequency (RF) spectrum coexistence. LTE is continuously refined and new features released. As the communications contexts for LTE expand, new research problems arise and include operation in harsh RF signaling environments and coexistence with other radios. Our testbed provides an integrated research tool for investigating these and other research problems; it allows analyzing the severity of the problem, designing and rapidly prototyping solutions, and assessing them with standard-compliant equipment and test procedures. The modular testbed integrates general-purpose software-defined radio hardware, LTE-specific test equipment, RF components, free open-source and commercial LTE software, a configurable RF network and recorded radar waveform samples. It supports RF channel emulated and over-the-air radiated modes. The testbed can be remotely accessed and configured. An RF switching network allows for designing many different experiments that can involve a variety of real and virtual radios with support for multiple-input multiple-output (MIMO) antenna operation. We present the testbed, the research it has enabled and some valuable lessons that we learned and that may help designing, developing, and operating future wireless testbeds.

Prototypes of using directional antenna for railroad crossing safety applications

In this demonstration proposal, we present a prototype of a rapidly deployable and cost-effective railroad crossing early warning system integrated with the railway system. Specifically, the proposed demonstration deal with the safety applications based on dedicated short range communications (DSRC) protocol and devices using our different antennas. We will demonstrate the feasibility and advantages of our proposed system, including the antenna design, system deployment, the over-the-air transmission, and the software applications that we developed for the end users1.