Nguyen, Brunstrom, Grinnemo, and Taheri
42
gaming, public safety, vehicular communications, and offloading, as shown in
Figure 2.6(b). However, there are a number of open issues that need to be solved in
the future, such as interference management, resource management services and
device discovery, security and privacy. Some other directions for future research
would be the integration of D2D communication with mmWave and massive
MIMO technologies.
2.3.1.5 Cloud‐based Radio Access Network
Cloud‐based Radio Access Network (Cloud‐RAN) is an ideal solution to design the
radio access part of 5G networks, since it enables energy efficiency, cost savings on
baseband resources, as well as improvements on network capacity, increased throughput, etc. [23]. The Cloud‐RAN is essentially the decoupling of the Remote Radio Head
(RRH) from the Baseband Unit (BU) of a base station, and the implementation of BU in
a centralized cloud computing environment. RRHs are connected to a BBU pool by
using high speed fiber or microwave‐link fronthaul networks. In fact, there are several
options to split the functionality of the base station, which refers to the RAN‐as‐a‐
Service (RANaaS) [24]. These two concepts are shown in Figures 2.7(a) and (b). This
simplified base station architecture is paving the way for dense 5G deployment by
making it affordable, flexible and efficient [25].
Apart from the benefits that Cloud‐RAN offers to the design of the 5G system,
there are various challenges that need to be overcome before fully exploiting its
benefits; such as fronthaul constraints and performance optimization, placement
optimization of RRHs, efficient scheduling and elastic scaling of BBUs in the
BBU pool. Some other research directions in the future could be the incorporation
of C‐RAN and distributed RAN (D‐RAN) or research on heterogeneous CRAN
(H‐CRAN).
2.3.1.6 Mobile Edge and Fog Computing
As we move to 5G, many of its services and applications will require very stringent
latency in the order of milliseconds. One of the most prominent solutions is to bring
the IT services and processing capabilities down to the edge of the mobile network,
within the RAN and in close proximity to mobile users. This refers to the concept of
Mobile Edge Computing (MEC) technology and its sibling Fog Computing.
Figure 2.8 illustrates the concept of MEC and its architecture. As specified in the
ETSI white paper [26] published 2015, the aim of MEC is to reduce latency, ensure
highly efficient network operation and service delivery, and offer an improved user
experience. With this capability, MEC will open new frontiers for network operators, application service providers, and content providers, by enabling them to
introduce innovative services and applications. Some typical examples of services
enabled by MEC are augmented reality, RAN‐aware video optimization, connected
cars, and IoT, etc. [26].
A similar concept to MEC is Fog Computing (FC) [27] defined by Cisco in 2012, a
paradigm in which cloud computing resources are extended to the edge of the network,
to create a highly virtualized platform that provides compute, storage, and networking
services between end‐devices and traditional data centers. Some of the prominent
features of FC, which are suitable for 5G communications, are low latency, location
42
gaming, public safety, vehicular communications, and offloading, as shown in
Figure 2.6(b). However, there are a number of open issues that need to be solved in
the future, such as interference management, resource management services and
device discovery, security and privacy. Some other directions for future research
would be the integration of D2D communication with mmWave and massive
MIMO technologies.
2.3.1.5 Cloud‐based Radio Access Network
Cloud‐based Radio Access Network (Cloud‐RAN) is an ideal solution to design the
radio access part of 5G networks, since it enables energy efficiency, cost savings on
baseband resources, as well as improvements on network capacity, increased throughput, etc. [23]. The Cloud‐RAN is essentially the decoupling of the Remote Radio Head
(RRH) from the Baseband Unit (BU) of a base station, and the implementation of BU in
a centralized cloud computing environment. RRHs are connected to a BBU pool by
using high speed fiber or microwave‐link fronthaul networks. In fact, there are several
options to split the functionality of the base station, which refers to the RAN‐as‐a‐
Service (RANaaS) [24]. These two concepts are shown in Figures 2.7(a) and (b). This
simplified base station architecture is paving the way for dense 5G deployment by
making it affordable, flexible and efficient [25].
Apart from the benefits that Cloud‐RAN offers to the design of the 5G system,
there are various challenges that need to be overcome before fully exploiting its
benefits; such as fronthaul constraints and performance optimization, placement
optimization of RRHs, efficient scheduling and elastic scaling of BBUs in the
BBU pool. Some other research directions in the future could be the incorporation
of C‐RAN and distributed RAN (D‐RAN) or research on heterogeneous CRAN
(H‐CRAN).
2.3.1.6 Mobile Edge and Fog Computing
As we move to 5G, many of its services and applications will require very stringent
latency in the order of milliseconds. One of the most prominent solutions is to bring
the IT services and processing capabilities down to the edge of the mobile network,
within the RAN and in close proximity to mobile users. This refers to the concept of
Mobile Edge Computing (MEC) technology and its sibling Fog Computing.
Figure 2.8 illustrates the concept of MEC and its architecture. As specified in the
ETSI white paper [26] published 2015, the aim of MEC is to reduce latency, ensure
highly efficient network operation and service delivery, and offer an improved user
experience. With this capability, MEC will open new frontiers for network operators, application service providers, and content providers, by enabling them to
introduce innovative services and applications. Some typical examples of services
enabled by MEC are augmented reality, RAN‐aware video optimization, connected
cars, and IoT, etc. [26].
A similar concept to MEC is Fog Computing (FC) [27] defined by Cisco in 2012, a
paradigm in which cloud computing resources are extended to the edge of the network,
to create a highly virtualized platform that provides compute, storage, and networking
services between end‐devices and traditional data centers. Some of the prominent
features of FC, which are suitable for 5G communications, are low latency, location