ISO 21212:2008 determines the air interface for second generation (2G) cellular networks and 2G systems (e.g. using WAP and I-Mode type protocols) to be compliant to CALM, i.e., requirements that must be met before a 2G system can be incorporated into a CALM system. In particular, it specifies protocols and parameters that 2G systems shall include to support prolonged, long-range, high data rate wireless communication links in ITS environments where heterogeneous handovers or media independent handovers (MIH) are either necessary to maintain the link, or desirable as determined by media selection policies.

ISO 21212:2008 provides protocols and parameters for long range, medium speed wireless communications in the ITS sector using second generation cellular communications.

Wherever practicable, ISO 21212:2008 has been developed by reference to suitable extant standards, adopted by selection. Required regional variations are provided.

Specifically, for ISO 21212:2008, extant 2G systems, as defined by various international and national standards, are adopted by reference.

Application-specific upper layers are not included in ISO 21212:2008, but will be driven by application standards (which may not be technology specific).