Page 147 - ITU Journal Future and evolving technologies – Volume 2 (2021), Issue 2

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

1 1
( ) = (( ) + ( ) + )(1 + ∑(1 − ) −1 )+

=1
1
′ −1
(1 + ∑(1 − ) ) .( ). + (1 + . ) . + .
=1
(14)
Scenario 5: Cloud‑RAN
Finally, let’s consider the scenario where operators join
forces to build a cloud and a dedicated front‑end link in
Fig. 2 – Site sharing by operators
which sites and masts are shared.
Scenario 3: Pylon sharing In [18], it is shown that, in a standard case, C‑RAN is not
Let us now consider, in addition to site sharing, tower more bene icial than traditional RAN in the context of ru‑
sharing at each site. ral areas. However, with the underutilization of resources
and the possibility that C‑RAN offers to share the resource
in the BBU pool, C‑RAN becomes bene icial when doing a
massive deployment. This is what justi ies the choice to
use a shared C‑RAN.

Fig. 3 – Sites and pylon sharing by operators

1 1
( ) = (( ) + ( ) + )(1 + ∑(1 − ) −1 )+
Fig. 5 – Cloud‑RAN sharing
=1

′ −1
(1 + ∑(1 − ) ) . , + (1 + . ) . + . In this scenario, another entity is added to the network;
=1 it is the fronthaul with a cost model similar to that of the
(13)
backhaul. Considering that the cost of an eNodeB is the
sum of the cost of a BBU and that, as shown in [24] , thanks
Scenario 4: Backhaul sharing to the cloud, we have a gain in global energy expenditure,
Let us now consider a scenario where operators join we have :
forces to build a common backhaul such as ibre or High‑
Altitude Platform Systems (HAPS) to go together to un‑
served areas. The operators share the CAPEX and OPEX ( ) = (( ) + ( ) + . + . )
′
costs. So the bandwidth of the platform is divided be‑

tween the operators for their personal use. The transmis‑ (1 + ∑(1 − ) −1 ) + (1 + ∑(1 − ) )
′
″ −1
sion infrastructure to be deployed will carry the various =1 =1
signals to and from the sites using appropriate multiplex‑ .( 1 ). + (1 + . ) .Δ. + . +
ing techniques. ℎ
(15)
ℎ : CAPEX cost of transmitter‑receiver equip‑
ment on fronthaul link
: the additional cost generated by the cloud.
Δ : the coef icient that is induced by the energy gain
n’: is number of BBUs
In rural areas, the traf ic used in the cells is generally very
low. Centralization of the BBU can allow ef icient use of
the resource in that, one BBU can support the traf ic of
several RRH through virtualization. Also, half of a BTS site
can be used for one RRH site. Let x be the number of RRHs
Fig. 4 – Backhaul sharing
using the resource equivalent of one physical BBU.

© International Telecommunication Union, 2021 133