This International Standard specifies general requirements for the provision of ITS services, using the CALM architecture and protocols, via the use of public wireless networks [including cellular telephony and mobile wireless broadband (MWB) systems]. In particular, this International Standard specifies protocols and parameters that public wireless networks shall include to support prolonged 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, and such handover is provided by the public wireless network. The requirements for the use of CALM via public wireless networks where there is no provision for heterogeneous cell/cell handover (i.e. so-called nomadic services) is not the central focus of this International Standard, but general requirements to enable the use of such systems, within the limits of the range of a single cell, are also provided. Wherever practicable, this International Standard has been developed by reference to suitable extant standards, adopted by selection. Required regional variations are provided. Specifically, for this International Standard, extant national and International Standards for public wireless networks are adopted by reference and are not redefined herein. Application-specific upper layers are not included in this International Standard, but will be driven by application standards (which might not be technology specific).