Page 228 - From GMS to LTE

214 From GSM to LTE-Advanced Pro and 5G

interface as it is a major task of the LTE base station. Afterward, basic procedures to
establish and maintain a data connection between a mobile device and the network are
discussed, followed by an overview of mobility management and power management
considerations. Network planning aspects and interconnection to GSM, UMTS and
CDMA networks are then discussed, followed by operational topics such as the use of
different backhaul technologies. This is followed by special topics such as network shar-
ing and the use of IPv6 in mobile networks, and emerging features such as the air inter-
face and core network enhancements for Narrow‐Band Internet of Things (NB‐IoT)
devices and Network Function Virtualization (NFV). At the end of the chapter, future
topics such as additional air interface enhancements for small cells and 5G radio and
core network evolution in 3GPP are discussed.

4.2 Network Architecture and Interfaces

The general LTE network architecture is similar to that of GSM and UMTS. In
principle, the network is separated into a radio network part and a core network part.
The number of logical network nodes, however, has been reduced to streamline the
overall architecture and reduce cost and latency in the network. Figure 4.1 gives an
overview of the LTE network and its components and the following sections give a
detailed overview of the tasks of the different nodes and how they interact with each
other. The subsequent sections then go on to describe the most important functional-
ity in more detail.

SGi
PDN-GW Internet
S5
CP UP

S6 S11
HSS MME Serving-GW

S1
CP UP

eNode-B X2 eNode-B
LTE Uu

Mobile device
Figure 4.1 LTE network overview.