ISO 21213:2008确定了适用于使用第三代（3G）蜂窝网络的CALM的空中接口选项。特别是，它规定了3G系统应包括的协议和参数，以支持其环境中的长距离、高数据速率无线通信链路，其中异构切换或媒体独立切换（MIH）是维持链路所必需的，或是由媒体选择策略决定的所需。 ISO 21213:2008提供了使用第三代蜂窝通信的ITS部门中远程、中速无线通信的协议和参数。 在可行的情况下，ISO 21213:2008是通过参考合适的现有标准制定的，通过选择采用。提供了所需的区域差异。 具体而言，对于ISO 21213:2008，参考采用了各种国际和国家标准定义的现有3G系统。 ISO 21213:2008中不包括特定于应用程序的上层，但将由应用程序标准（可能不是特定于技术）驱动。

ISO 21213:2008 determines the air interface options applicable to CALM using third generation (3G) cellular networks. In particular, it specifies protocols and parameters that 3G 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 21213:2008 provides protocols and parameters for long range, medium speed wireless communications in the ITS sector using third generation cellular communications. Wherever practicable, ISO 21213:2008 has been developed by reference to suitable extant Standards, adopted by selection. Required regional variations are provided. Specifically, for ISO 21213:2008, extant 3G systems, as defined by various international and national standards, are adopted by reference. Application specific upper layers are not included in ISO 21213:2008, but will be driven by application standards (which may not be technology specific).