The automotive industry is currently exploring multi-vehicle safety applications. These safety applications assume a robust, mobile, low-delay, high reliability wireless communication technology to create mobile ad-hoc networks (MANets). Safety applications warning nearby vehicles of dangerous conditions require periodic monitoring for warning signals. Although these warnings may not be data intensive, they are time critical and must be reliably received in challenging wireless enviroments. Although a channel has been reserved for safety communications, the challenge is to monitor for time critical safety warnings during on going non-safety related communications. The simplest means to do this is to have a separate receive radio constantly monitoring for vehicle to vehicle safety messages but this is probably not the most elegant nor cost effective technique. Our research seeks to investigate alternative and more efficient techniques to monitor for safety communications and to characterize the wireless channel for vehicular communications.
The Dedicated Short Range Communications (DSRC) standard leverages current 802.11a WLAN protocols to create a standard for vehicular communications. One of our first tasks is to develop a DSRC software defined radio platform for investigating various MAC and PHY improvements to implement reliable safety applications. The software defined radio (SDR) affords the most flexibility in investigating and prototyping a variety of solutions. Because the basis of the DSRC standard is in WLAN networking, it is not optimized to handle the short but very urgent safety messaging scheme. The SDR will utilize flexible and broadband radio frontends coupled with software implementations of baseband and MAC functions to explore research in improving safety based communications. This will provide a platform that can be adapted to new emerging technologies and to explore alternative topologies and algorithms. The SDR will be a platform to test improved modulation formats (including novel and new ways of using OFDM), multi-band down conversion protocols, and architectures more suitable for safety applications. Instead of being fixed to hardware implementation of the baseband functions, a software radio will allow rapid investigation and prototyping of new algorithms and real world testing of the research. The radio will be based upon current technology and will be coupled with custom software to implement the research platform.
The environment for vehicular communications is both varied and complex. Signals are equally likely to traverse wide open spaces and urban labyrinths. Users can be at a standstill or traveling at highway speeds. Channel models must be able to characterize the problems of multipath, doppler, and fading. We are developing our models using real physical measurements of representative environments. By understanding the impairments to the channel, we gain insight into improvements to the PHY layer for DSRC communications.