Rajib Taid - Mobile Communications Systems Development

1 Visit the 3GPP site [2].

2 Select a subject/area and the particular technical specification series. Select a technical specification of interest to download. Click on the Click to see all versions of this specification to download a specification for a particular release.

An introduction of a new feature as part of a release is documented in the form of a Change Request . The affected technical specifications due to a new feature are captured under a particular Change Request. Given a Change Request number, the affected technical specifications may be downloaded from the 3GPP portal https://portal.3gpp.org/ChangeRequests.aspx. One can find the relevant changes introduced in each affected technical specification due to a new 3GPP feature.

Many technical documents (TDocs) in the form of written contributions are produced as a result of various meetings held among the 3GPP technical specifications working groups mentioned in Section 2.5.2and other stakeholders. To produce a version of a technical specification, numerous meetings are held. Visit the 3GPP site [2] and follow the steps mentioned in the previous section. Click on the tab Versions . Look at the Meetings column under a particular Version . Click on any Meeting number to display the various written contributions (TDocs) under the “List of TDocs” link. A TDoc or a written contribution contains highly technical discussions, observations, and proposals, in a particular area/topic of the concerned technical specification. One can acquire a great deal of knowledge from such a TDoc, which can be used as supplementary information. If a particular aspect is not clear from a technical specification, a TDoc may be referred for more information on the related area.

The 3GPP technical specifications are organized into different versions called “ releases ”, such as Release 99, Release 4, Release 5, Release 6, Release 7, Release 8, Release 9, Release 10, Release 11, Release 12, Release 13, Release 14, Release 15 and beyond. Various features introduced in each 3GPP releases are summarized in Table 2.3.

Some of these 3GPP releases involve the SAE right from the GSM to the 5G system as described earlier in Section 2.3. However, some of these releases involve the introduction of additional features only to improve the existing data transmission rates. New functionality or enhancement to an existing release is also added in each subsequent release. The Release 99, shown in Figure 2.10, was the first version where UMTS came into existence which evolved from the GSM/GPRS system in terms of the new RAN, UTRAN. Subsequent releases of the UMTS UTRAN introduced new features offering increased data transmission rates. Similarly, 3GPP Release 8 was the first version of the LTE system, and Release 15 was the first version of the 5G system.

Table 2.3 Summary of 3GPP Releases and their features.

Prior to Release 99, 3GPP technical specifications releases were known by the corresponding year such as Release 1997 and Release 1998. However, after the Release 99, 3GPP technical specifications releases are known by the corresponding version number only such as Release 4 Release 5 and beyond. A new 3GPP release details are described through its own and dedicated technical specifications series. However, because of a new feature or functionality, an existing technical specification from a previous release version may be also impacted. Details of such information can be derived from the 3GPP release descriptions document available on the 3GPP site [3].

Apart from the introduction of a new feature in each 3GPP release, a new message(s) or a new information element(s) or a new type of channel, either in DL or UL, to an existing protocol layer may be also added. For further details on each of the above releases, visit this 3GPP site [3].

In this chapter, we have presented the introductory architectures, the various domains or areas, and the network elements of mobile communications networks based on the GSM, UMTS, and LTE systems. The 5G system is also covered in appropriate sections of this chapter. We then presented the global 3GPP standardizations process of various technical specifications based on which mobile communications systems and networks are designed and built. The evolutions of mobile communications systems and networks in terms of 3GPP system architectures release are also discussed.

The reader is advised to get familiar with the various aspects of a 3GPP TS. To start with, select a particular mobile communications system and then use the 3GPP specification series [2] as the guiding resources to download and study the technical specifications of a particular series and the subject area of interest. Get an overview of the various protocol layers, interfaces, procedures, and functions performed by a particular network element.

This chapter was the introductory one, for the reader, whose contents are general in nature and thus applicable to the 5G system also. The various protocols, procedures, and functions performed by a mobile communications network and its elements/entities shall be described in detail in the subsequent chapters of this book. Design, development, and implementation aspects of a network element in the software code shall be also presented in the subsequent chapter.

This 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.