Page 15 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 6 – Wireless communication systems in beyond 5G era

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 6

edge. The RN is wirelessly connected to a Donor eNodeB
CS (DeNB), so that the donor cell provides shared radio re‐
GSM/GPRS
networks sources between the UEs (not served by the DeNB) and
the DeNB. In parallel, the D2D paradigm [8], [9] was men‐
Core network tioned in LTE Advanced in order to enable direct com‐
WCDMA/ Circuit core munications between UEs, without going through the eN‐
HSPA domain odeB and the core network. However, the implementa‐
User IMS domain tion and diffusion of D2D communications has remained
management in a very preliminary phase. With the advent of LTE, there
was also a signi icant improvement for public safety net‐
Packet core
LTE works [10]. The original limitations to voice services be‐
domain
gan to expand to more general broadband communica‐
tions such as multimedia sharing, video calls, and live‐
video streaming. Finally, even if some preliminary pro‐
IP
Non-3GPP posals were provided for deploying LTE in aerial net‐
networks
works [11], the LTE has remained a fully terrestrial wire‐
less cellular network.
Fig. 1 – Domains in the 3GPP architecture of the evolved packet system [6].
2.2 The dawn of cloud computing and the
within the different domains. The circuit core domain
standardization of softwarized networks
consists of nodes and functions that provide support for
circuit‐switched services over GSM and Wideband Code‐
Division Multiple Access (WCDMA). The vision of 5G was not an agnostic and independent de‐
sign project and standardization effort. For the irst time
Next, the packet core domain consists of nodes and func‐ in the panorama of telecommunications, a wireless cellu‐
tions that provide support for packet‐switched services. lar network absorbed the very novel paradigms in com‐
The packet core domain also provides functions for man‐ puting and networking in order to move towards a real
agement of the Quality‐of‐Service (QoS). The IMS breakthrough with the previous evolution. Concepts like
includes equipment and functions that provide support cloud computing, and SDN and Network Function Virtu‐
for mul‐timedia sessions. In the L TE RAN there are alisation (NFV), radically shaped the idea of a communi‐
base sta‐tions called eNodeB. All eNodeBs are cation network, as previously meant. This revolution in
connected to at least one Mobility Management Entity communications also inherently changed the procedure
(MME), which han‐dles all control plane signalling. The of standardization of wireless cellular networks. From
IP packets lowing to and from mobile devices are 5G onwards, the standardization of wireless networks has
handled by two logical nodes called the Serving become a global and collective effort of several standard‐
Gateway (S‐GW) and the Packet Data Network Gateway ization bodies, collaboratively and complementary work‐
(PDN‐GW). The S‐GW is the an‐chor point for intra‐ ing towards the same target. Fig. 2 depicts the standard‐
L TE mobility, as well as for mobil‐ity between GSM/ ization effort of 5G, led by 3GPP and ITU, and cooper‐
General Packet Radio Service (GPRS), WCDMA/High atively supported by the major standardization bodies
Speed Packet Access (HSPA) and L TE. The S‐GW also worldwide.
buffers downlink IP packets destined for ter‐minals
that happen to be in idle mode, as well as supports
transport level QoS through marking IP packets. On the Internet
protocols
other hand, the PDN‐GW is the point of interconnection to
external IP networks. The PDN‐GW includes functional‐ Cross reference Referring to specs
Cross reference
ity for IP address allocation, charging, packet iltering and
policy‐based control of user‐speci ic IP lows. The PDN‐ IMT Mobile applications
requirements Requirements 3GPP market
GW also has a key role in supporting QoS for IP services. partners
Terminal certification
The latest releases of L TE also included new connec‐ Partners based on 3GPP specs
Reference to referrring to
tion paradigms that were becoming quite popular in the 3GPP specs 3GPP specs for
local
deployment
technical and scienti ic community such as relaying and
Device‐to‐Device (D2D). L TE also opened the way to cellu‐ EU Japan Korea China US India
lar networks with base stations of different coverage size.
This meant the coexistence of large and small cells with
the deployment of the Relay Node (RN), a lower power Fig. 2 – Structure of the standardization effort of 5G [1].
3GPP base station enhancing the coverage at the cell’s

© International Telecommunication Union, 2021 3