Page 67 - Kaleidoscope Academic Conference Proceedings 2021

Connecting physical and virtual worlds

User’s place Antenna site Operator’s building Antenna sites Operator
building
(a) Virtualized RAN in 5G and advanced 5G AP URIC

UE vDU vCU AP cluster URIC
RU URIC
UE UE AP sub-cluster Service
vDU vCU Core #1 vAP
UE vCPU A
#2
Cell vDU vCU #3
● vCPU vCPU B
RAN slice Virtualized ●
for each communication service
● vCPU Ｃ
(b) User-centric RAN in Beyond 5G #m Low-RAN slices High-RAN slices
vAP
UE vAP vCPU Figure 5 – RAN slicing
vAP
Core
vAP efficiency by a user multiplexing and satisfy the user’s
UE vAP vCPU required communication quality. Hence, the period of the
vAP High-RAN slice management will be from minutes to tens of
Virtualized minutes. Since the divided RAN slice can realize their
AP is virtualized, and a logical network management with an appropriate period, mobile
with cell-free is managed for each UE.
communications with CF-mMIMO can be provided in the
CU: Central Unit, DU: Distribution Unit, RU: Radio Unit, user-centric RAN.
UE: User equipment, CPU: Central Processing Unit,
AP: Access Point, vXX: virtualized function of XX
The second extension is the management scheme for the
Figure 4 – RAN structure user-centric RAN. To assume large-scale deployment of the
user-centric RAN such as an urban area, a huge number of
mentioned that all APs were multiple CPUs and the transport distributed RAN resources such as computing resources and
link capacity between the CPUs and APs. To satisfy the transport links will be managed. In addition, multiple
quality requirements anytime, anywhere, the user-centric virtualized APs and CPUs on the computing resources will
RAN management should be able to build networks per users be managed. The virtualized APs and CPUs are distributed
flexibly from the existing CPUs and APs. The management over the RAN as shown in Figure 4 –(b), because only one
includes a resource assignment for each network built, such CPU can process CF-mMIMO signals from several APs in
as computing resources, transport link resources, and radio the RAN due to the limited computing resources. We defined
resources which includes not only a scheduling of radio links a User-centric RIC (URIC) to manage a large number of the
but also a selection of APs for each user. It will also be AP clusters and the AP sub-clusters in the user-centric RAN.
performed based on many network statuses, such as traffic The URICs will be placed in a distributed manner to manage
occasions from users, usage of resources, and wireless link the large-scale user-centric RAN. They control interference
qualities for each user etc. between the AP clusters or the AP sub-clusters by their
management to obtain homogenized quality in wireless links
To realize the above management, two extensions are for CF-mMIMO. The other controls are the formation of the
required to apply the virtualized RAN technology to the user- High-RAN slice or the Low-RAN slice, RAN resource
centric RAN shown in Figure 4 –(b). To process CF- management for the slices, and RAN function replacement
mMIMO signals, we define two set types of APs: (1) “AP for vCPUs or vAPs etc. Those controls are important to
cluster” is a set of APs accommodated by each CPU, and (2) satisfy the user’s quality requirements of communication
“AP sub-cluster” is the subset of the AP cluster that services both anytime and anywhere. To realize the above
cooperatively transmits and receives data with each user. The managements, it requires interfaces for exchanging
first extension is the current virtualized RAN structure to information and sending messages, regarding how to place
handle the AP cluster and AP sub-cluster. Figure 5 shows our the URICs and control algorithms. The details of the new
proposed RAN slicing for the user-centric RAN. The RAN virtualized RAN structure and the management scheme
slice is divided into two areas called the “Low-RAN slice” described in this section will be examined further in the next
and “High-RAN slice”. The Low-RAN slice is formed for step.
each user to manage an AP sub-cluster. Since the AP sub-
cluster needs to be managed according to the status of each 3.3 Key technology 3: Virtualized terminals using
user, e.g., position, characteristics of wireless channel, usage terahertz communications
of application etc., the period of the management will be tens
or hundreds of milliseconds. The High-RAN slice is used for In this section, we explain the specific configuration of the
managing the AP cluster and RAN functions. Such proposed virtualized terminal using terahertz
management is similar to the current management in the communications for user-centric RAN architecture. To
virtualized RAN to maintain both high resource utilization realize CPS for Beyond 5G, it is necessary to increase the

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