Page 100 - Kaleidoscope Academic Conference Proceedings 2020

2020 ITU Kaleidoscope Academic Conference

Table 4 – Different Choices for 5G CN Deployment [4, 6].
Choice Virtualization Separation Year Notes
• Reference point interfaces (Sx interfaces)
Rel. 8-13 • Proprietary protocols (e.g., Diameter, eGTP, S1AP, and PFCP) for each interface
EPC Optional Disabled
(2008-2016) • Possibility of deploying DECOR
• Some nodes/NFs should be upgraded prior to 5G NSA deployment
• Reference point interfaces (Sx interfaces including Sxa, Sxb, and Sxc depending on CUPS)
Rel. 14-16
EPC+ Mandatory 3GPP CUPS (2016-2019) • Proprietary protocols (e.g., Diameter, eGTP-C, eGTP-U, S1AP, and PFCP) for each interface
• Possibility of deploying DECOR
• Some nodes/NFs should be upgraded prior to 5G NSA deployment
Designed • Service-based interfaces for CP function group (Nx naming for interfaces (e.g., Nsmf, Namf)),
using HTTP/2-based REST APIs
Rel. 15-17
5GC Mandatory separately (2016-2021) • Reference point interfaces for UP NFs and their interconnections (e.g., N1, N2, N4, and N9),
from the
using proprietary interfaces such as EPC
beginning • Supports network slicing (slice-based session establishment)
Table 5 – Different Stages for 5G CN Deployment [6, 8, 18].
State State# Description 3GPP Option
Initial ini1 Physical EPC Option 1
(2017-2020) ini2 Virtual EPC Option 1
ini3 Physical and virtual EPC (both serving 4G) Option 1
int1 EPC+ (serving both 4G and 5G Option 3) Option 3
int2 Virtual EPC (serving 4G) interworking with EPC+ (Serving 5G Option 3) Option 3
Intermediate int3 Virtual EPC (serving both 4G and 5G Option 3 (with less capacity)) Option 3
(2019-2023) int4 Physical EPC (serving 4G) interworking with virtual EPC (serving 5G Option 3) Option 3
int5 Physical EPC (serving 4G) interworking with EPC+ (serving 5G Option 3) Option 3
fin1 Physical EPC (serving 4G) interworking with 5GC (Serving 5G Options 2/4) Options 2/3/4
Final fin2 Virtual EPC (serving 4G) interworking with 5GC (Serving 5G Options 2/4) Options 2/3/4
(2020-2025) fin3 EPC+ (serving 4G) interworking with 5GC (serving 5G Options 2/4) Options 2/3/4
fin4 Unified 5GC (serving both 4G and 5G Options 2/4) Options 2/4

will be followed in the SA mode by implementing 5GC in 5.1 Capacity Considerations
KT’s core sites and provision of interworking with EPC+ Initial deployment of 5G TN is in the NSA mode with eMBB
(i.e., fin3). In this way, KT will support 4G, 5G NSA, and 5G services. Hence, gNBs require extensive transport capacity
SA devices [8, 18]. KT’s deployment strategy has also been to carry users’ data. In general, each 4G BS in urban areas
adopted by some other top-tier operators. Another option, injects about 150 Mbps to 1 Gbps traffic into the TN, but 4G
called unified 5GC, is to transit from fin3 to fin4, where 5G traffic will increase to about 600 Mbps to 20 Gbps in 2025
can use existing virtualized elements of 2G, 3G, and 4G core [19]. It is evident that existing TNs are totally inadequate for
networks. 5G and their capacity must be significantly increased.
Mid-tier Operators: It is advisable that mid-tier operators
deploy virtualized EPC sites (i.e., ini2 and ini3) to provide Suitable transport technologies must be adopted to support
service to 5G NSA devices in their respective areas. When the increase in traffic. The choice is impacted by existing
SDN and NFV are extensively deployed, the CN can be fiber networks, base station deployments, and availability of
upgraded to fin2 stage by virtualizing physical EPC sites spectrum. In general, fiber-based TNs support very high data
and provision of interworking with new 5GC sites (i.e., fin2) rates with low latency and high availability, but require high
[6, 8]. When Option 3 is chosen to support 5G NSA devices, CapEx. Additionally, permits from municipalities and other
a small software upgrade is needed in physical/virtual EPC authorities are needed, and installation and commissioning
nodes/NFs to add/modify a few parameters [8]. Moreover, the may take a long time. Wireless TNs are advantageous
S1-U interface capacity in the back-haul must be increased. as their CapEx is reasonable, and wireless installation and
Another choice is to upgrade vEPC sites to EPC+, which commissioning is much faster than fiber, but wireless TNs
improves scalability and flexibility of the network (i.e., int1, are inferior in terms of capacity, latency, and availability.
int2, and int5), to be followed by fin3 or fin4 as the final stage. Fiber-based TNs will be on the rise in the future, but wireless
Low-budget Operators: These operators may continue with TNs will also play an important role in 5G TNs [19]. The
physical EPC sites to support 4G (i.e., ini1), and deploy SDN followings should be considered in deploying TNs for 5G:
and NFV in their networks as prerequisites for 5GC to support • Replacing Wireless with Fiber in TN: Even 4G traffic is
5G SA devices (i.e., fin1). However, interworking between on the rise and hence a fiber-based TN is very desirable,
5GC and physical EPC sites is challenging due to capacity which can also be used in 5G networks with higher traffic
and other constraints when some intermediate deployment volumes. The primary candidate for fiber deployment
states are not implemented.
locations is 4G eNBs in dense urban areas, which may
already be experiencing bottlenecks in the TN. These eNBs
5. TRANSPORT NETWORK DEPLOYMENT
are generally situated in the best locations for deploying
In this section, we briefly review some possible choices gNBs. Since the implementation of fiber-based TN is time
for 5G TN deployment, and describe different options for consuming, network operators need to plan and implement
increasing bandwidth, C-RAN adoption, and implementation fiber-based TN in different steps in a timely manner, i.e.,
of transport SDN (T-SDN). 1-2 years prior to 5G commercial deployment [15].

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