Borman Expressway Point-to-Point Wireless Modem

The Federal Highway Administration has a nationwide allocation of five frequency pairs in the 220-222 MHz Narrowband Radio Services band which are intended for application in Intelligent Transportation Systems. These frequencies are available for use by state DOTs (subject to FHWA approval) and provide an attractive solution for certain low to medium bit rate data communications applications. However, given the limited bandwidth available in these channels, very efficient modems will be required to make maximum beneficial use of this resource. The goal of this project was to design, field test, and deploy a digital radio which uses the 220-222 MHz spectral allocation and is suitable for stationary point-to-point data communications applications. The target application for this project was the control (pan, tilt, and zoom) of a video camera located at the interchange of I-65 and the Borman Expressway. The wireless link extends from the camera location to the traffic operations center (approximately 1.5 miles). There were three main tasks needed to produce a deployable modem: 1) interface circuitry was required between the 220 MHz modem and the camera control keypad and the camera pan/tilt/zoom receiver, 2) the fabrication of a compact and rugged transmitter was required, and 3) the fabrication of a compact and rugged receiver was required. The receiver size constraints were more exacting than those of the transmitter as the receiver is deployed in a roadside cabinet, while the transmitter is deployed in the traffic management center. The work plan was divided into a set of twelve tasks. The 220 MHz modem can serve INDOT as a general purpose link for low to medium rate data communications in a wide variety of applications. The most significant issue outstanding with regard to widespread implementation of the technology is the mass production cost and the availability of a reliable source of production versions of the device. Efforts are continuing at both Purdue and Ohio State toward further simplifications aimed at complexity reduction in the receiver. As topics for further study, the following should be considered: 1) a detailed cost/benefit analysis should be made comparing the 220 MHz technology to other alternative technologies, and 2) a preliminary design study of interoperability issues should be performed for the 220 MHz technology in transportation applications

Like Deck Chairs on the Titantic: Why Spectrum Reallocation Won\u27t Avert the Coming Data Crunch But Technology Might Keep the Wireless Industry Afloat

Skyrocketing mobile data demands caused by increasing adoption of smartphones, tablet computers, and broadband-equipped laptops will soon swamp the capacity of our nation\u27s wireless networks, afact that promises to stagnate a $1 trillion slice of the nation\u27s economy. Among scholars and policymakers studying this looming spectrum crisis, consensus is developing that regulators must swiftly reclaim spectrum licensed to other industries and reallocate those rights to wireless providers. In this interdisciplinaryp iece, we explain in succinct terms why this consensus is wrong. With data demands increasing at an exponential rate, spectrum reallocation plans that promise only linear growth are destined to fail. What regulators should focus on, instead, are policies that encourage the sluggish incumbents presently dominating the wireless industry to roll out new networking technologies (like tiered network architectures, cognitive radio, and multicell MIMO) that together may allow exponential increases in spectral efficiency

28-GHz Channel Measurements and Modeling for Suburban Environments

This paper presents millimeter wave propagation measurements at 28 GHz for a typical suburban environment using a 400-megachip-per-second custom-designed broadband sliding correlator channel sounder and highly directional 22-dBi (15 degrees half-power beamwidth) horn antennas. With a 23-dBm transmitter installed at a height of 27 m to emulate a microcell deployment, the receiver obtained more than 5000 power delay profiles over distances from 80 m to 1000 m at 50 individuals sites and on two pedestrian paths. The resulting basic transmission losses were compared with predictions of the over-rooftop model in recommendation ITU-R P.1411-9. Our analysis reveals that the traditional channel modeling approach may be insufficient to deal with the varying site-specific propagations of millimeter waves in suburban environments. For line-of-sight measurements, the path loss exponents obtained for the close-in (CI) free space reference distance model and the alpha-beta-gamma (ABG) model are 2.00 and 2.81, respectively, which are close to the recommended site-general value of 2.29. The root mean square errors (RMSEs) for these two reference models are 9.93 dB and 9.70 dB, respectively, which are slightly lower than that for the ITU site-general model (10.34 dB). For non-line-of-sight measurements, both reference models, with the resulting path loss exponents of 2.50 for the CI model and 1.12 for the ABG model, outperformed the site-specific ITU model by around 14 dB RMSE

Graphite-protected CsPbBr3 perovskite photoanodes functionalised with water oxidation catalyst for oxygen evolution in water

Metal-halide perovskites have been widely investigated in the photovoltaic sector due to their promising optoelectronic properties and inexpensive fabrication techniques based on solution processing. Here we report the development of inorganic CsPbBr3-based photoanodes for direct photoelectrochemical oxygen evolution from aqueous electrolytes. We use a commercial thermal graphite sheet and a mesoporous carbon scaffold to encapsulate CsPbBr3 as an inexpensive and efficient protection strategy. We achieve a record stability of 30 h in aqueous electrolyte under constant simulated solar illumination, with currents above 2 mA cm−2 at 1.23 VRHE. We further demonstrate the versatility of our approach by grafting a molecular Ir-based water oxidation catalyst on the electrolyte-facing surface of the sealing graphite sheet, which cathodically shifts the onset potential of the composite photoanode due to accelerated charge transfer. These results suggest an efficient route to develop stable halide perovskite based electrodes for photoelectrochemical solar fuel generation

Evaluation Procedures for Deploying Spread Spectrum Interconnect

This purpose of this project was the design and construction of a testbed network for experimentation with spread spectrum communications in the 900 and 2400 MHz band. The current network consists of five fixed nodes and two portable nodes. Of the fixed nodes, three are located in the Purdue MSEE building, one is located in the Harold L. Michael Traffic Operations Laboratory, and one is located in the experimental traffic signal cabinet at the intersection of Stadium and Northwestern Avenues in West Lafayette. The testbed has been used to evaluate spread spectrum radio technologies from vendors Microwave Data Systems, GINA, and EnCom, as regards radio performance as a function of link distance and with varying levels of interference. The project has produced software that can be used to test any radio presenting a standard RS-232 interface to customer equipment. The testbed can also be interfaced with wireless channel emulator equipment located in the Wireless Communications Research Laboratory in order to test radio performance in multipath and fading environments. The field tests conducted to date have yielded the following conclusions regarding the design of spread spectrum interconnect for the traffic signal control application. First, as regards the need for line-of-sight between radio antennas, we were able to establish a link even when line of sight was not available although the resulting communication was somewhat error prone. If an additional robust protocol were designed these radios could work even in non-line-of-sight applications. The protocol would need to emphasize an efficient retransmission scheme as opposed to the use of more powerful forward error control codes (this observation comes from the link error statistics gathered from field testing). Second, it was noted that the RSSI (which stands for received signal strength indicator) value was not a completely informative measure of link quality. In other words, the link testing software found many instances of links where RSSI was relatively large yet many errors were incurred. Such situations always involved interference or suspected interference. Third, as regards the choice of antenna (Yagi versus omni) it is concluded that Yagi antennas (with their higher gain) were preferable in long distance rural environments. But in the presence of multipath propagation or interference (as in a town or city scenario) the omni was often preferable. Finally, interference tests showed that the MDS 9810 handled the interference well at the price of the throughput; the EnCom radio had a high throughput but also a high data loss rate in certain situations. It was concluded that if the application only needs between 6 and 14 kbps, the MDS radio is an ideal choice. For higher rate applications the EnCom radio would be preferred