CALM: CALM stands for Communication Access for Land Mobile
CALM enables the following communication modes:
- Vehicle-to-Infrastructure (V2I)
- Vehicle-to-Vehicle (V2V)
- Infrastructure-to-Infrastructure (I2I)
Methods of transmission used by CALM can be any one of these :
· DSRC 5.8-5.9 GHz (legacy systems)
· IEEE 802.11 standard
DSRC: Dedicated short-range communications
DSRC :One-way or two-way short-range to medium-range wireless communication channels specifically designed for automotive use, it consists of a collection of standards for all OSI layers and still some are in review phase
EN 12253:2004 :Physical layer using microwave at 5.8 GHz
EN 12795:2002 :DSRC Data link layer: Medium Access and Logical Link Control
EN 12834:2002 :Application layer
EN 13372:2004 :DSRC profiles for RTTT applications
EN ISO 14906:2004:Application interface
In October 1999: FCC: allocated 75 MHz of spectrum in the 5.9 GHz band to be used by intelligent transportation systems (ITS).
In August 2008: ETSI allocated 30 MHz of spectrum in the 5.9 GHz band for ITS.
· Two intersection RSE messages enable a suite of intersection-related safety applications.
· SPaT message - Signal Phase and Timing
· MAP message – Intersection geometry
· Other RSEs can send Traveler Information message on curve speed, height restriction, icy roads, etc.
· IP data exchange with servers in the Internet – RSE acts as forwarder
· Each vehicle broadcasts its core state information in a “Basic Safety Message” (BSM) nominally 10 times/sec.
· BSM is sent in 360o pattern using IEEE 802.11p technology.
· Upon receipt of BSM, vehicle safety host builds model of each neighbor’s trajectory, assesses threat to host vehicle, warns driver (or takes control) if threat becomes acute.
DSRC ppt from https://mentor.ieee.org