Cisco Systems says it agrees with the National Highway Traffic Safety Administration (NHTSA) that Dedicated Short Range Communications (DSRC) is the only mature communication option for vehicle communication-based crash avoidance. But the company says it’s important to recognize there may be a future non-DSRC radio-based technology to address safety.
Cisco, which has been actively working with the auto industry on in-vehicle networking and cloud services, told the NHTSA that DSRC technology, and in particular Basic Safety Message (BSM), has undergone extensive testing under the direction of the U.S. Department of Transportation (DoT) and has been deployed in an array of demonstration projects. A number of vendors offer DSRC, and it’s now shipping as standard equipment in GM Cadillac CTS models.
That’s not to say cellular-based systems don’t hold great promise. However, the company said, that application is not as mature as DSRC is today. Until recently, the standards on which 4G LTE systems are based could not reasonably address radio-based communications safety for vehicles and deficiencies were many, the company says.
The situation is beginning to change with industry adoption of new cellular standards for Vehicle to Vehicle (V2V), and “we are beginning to see the first testing initiatives for safety applications of the new radios that are based on these standards, including radios that enable direct V2V communication without routing transmissions through infrastructure,” Cisco states. “That said, extensive testing of this technology by U.S. transportation regulators to verify its fitness for purpose and crash avoidance properties has not begun as of the time these comments are being submitted. Nor has there been engagement of state DoTs to understand the proposed new cellular V2V system, how it may differ from DSRC, and the resulting impact to state DoT plans and goals.”
Plus, there’s the issue of business models and whether the cellular radio is built into the purchase price of the vehicle, as well as issues around liability, subscription fees and more.
Still, Cisco cautions that for NHTSA, the decision to move ahead with a DSRC BSM approach does have consequences should newer technologies later be presented as substitution candidates.
“Having multiple non-interoperable systems communicating with subsets of the national fleet will produce sub-optimal results in terms of crash avoidance,” the company stated. “Should there come a time when a new V2V technology presents itself as a viable candidate to replace DSRC (as the new V2V cellular technology might), policymakers would have to have a plan to migrate vehicles from the DSRC-based system to the new system.”
There are multiple ways a migration strategy might be implemented, but the company said the important thing to understand is the two radio technologies—cellular and DSRC—are today different and a DSRC BSM message transmitted from one vehicle to a different vehicle equipped with a cellular-based technology would not be received in a meaningful, actionable form and vice versa.
Meanwhile, the FCC issued a Notice of Proposed Rulemaking (NPRM) in early 2013 that proposed allowing a portion of the DSRC band to be shared with unlicensed devices such as 802.11.
Cisco and Qualcomm have suggested opposing plans for how the band should be shared. Qualcomm has promoted the idea of moving safety-related DSRC to a segment at the top of the band and leaving the lower portion to be shared by Wi-Fi and non-public safety-related users.
Cisco has championed a sharing proposal it calls “detect and vacate” that relies on the ability of 802.11ac devices to react to 802.11p “short training symbols” that precede the transmission of the BSM. The “detect and vacate” method of sharing is now being tested in prototype at an FCC lab.