Borman Expressway Point-to-Point Wireless Modem

摘要

The Federal Highway Administration has a nationwide allocation of five frequencypairs 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, ver 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.