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3 Protocols, Interfaces, and Architectures Introduction
ОглавлениеThis chapter covers the protocol architectures of network elements of mobile communications networks based on the Global System for Mobile Communication (GSM), Universal Mobile Telecommunication System (UMTS), Long‐Term Evolution (LTE), and 5G systems as defined by the 3rd Generation Partnership Project (3GPP). The protocol stack, its layer, and the architecture of a mobile communications network are different from the traditional Internet Protocol (IP) networks. Nevertheless, the protocol stack and layers of a mobile communications network can be studied in parlance with the OSI‐7‐layer reference network architecture. Developers must have understandings of the architectural aspects of protocol stack and its layers as it is core to the design and development of network elements of mobile communications systems and networks.
We begin with the basic means of communication between two peer protocol layers of network elements irrespective of the mobile communications system and network being used. Following this, we present the concept of sublayering of a protocol layer performing different functions and procedures of each protocol sublayer. We then present how protocol layers are grouped in case of the UMTS, LTE, and 5G systems based on the peer‐to‐peer communication between a User Equipment (UE) and the radio access network (RAN) and between UE and core network (CN). Classification of individual protocol layers is also presented based on the nature of functions performed by each layer. We also present the working model of a protocol layer based on which it provides services to its upper layer or uses the services from a layer below it. We close this chapter with another aspect of peer‐to‐peer protocol layer communications, which is protocol layer termination.