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 :
· Infrared
· GSM
· DSRC 5.8-5.9 GHz (legacy systems)
· IEEE 802.11 standard
· Bluetooth
· RFID
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
Background:
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.
V2I (Vehicle-to-Infrastructure)
· 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
V2V(Vehicle-to-Vehicle)
· 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.
Ref:
http://en.wikipedia.org/wiki/Dedicated_short-range_communications
http://en.wikipedia.org/wiki/Communications,_Air-interface,_Long_and_Medium_range
DSRC ppt from https://mentor.ieee.org
