Читать книгу Mobile Communications Systems Development - Rajib Taid - Страница 70

In the previous section, we have mentioned about the classifications of protocol layers into the control plane or signaling and user plane. In the case of UMTS, LTE, and 5G systems, their air interface control plane or signaling protocol layers are further grouped into what is called the Access Stratum (AS)) and NAS layer. The word “Stratum” means a grouping of protocols that is related to one service aspect of the various services provided by one or several network elements. The LTE, 5G, and UMTS system air interface protocol layer groupings are illustrated in Figure 3.9.