Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 56 (2023)
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Wi-Fi service in the RIBF experimental area
H. Baba,∗1 H. Honda,∗2 and M. Kurokawa∗2Outer
Conductor

SheathInner
Conductor

B1F

B3F

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Internet service is one of the essential infrastructures
for research activities. For information security, networks are required to be separated depending on users
and purposes. In the RIBF, an easy-to-use and secure network environment is necessary because many
external researchers participate in experiments one after another. For example, a dedicated network has
been constructed in the RIBF experimental area fordata acquisition during experiments using the BigRIPS
beam line. However, access to the Internet is accessed
through RIKEN’s intranetwork, and there are concerns
about network separation for external researchers.
To achieve secure network separation, Eduroam andguest Wi-Fi services provided by RIKEN Information
System Divisions for external researchers were introduced in the B1F and B3F measurement rooms of theRIBF experimental area. The B1F and B3F measurement rooms (each ﬂoor has an area of approximately
2000 m2 ) are located apart from each other, and somerooms are separated by walls. This required the installation of a large number of wireless access points toprovide wireless signals to the entire area. By adopting
leaky coaxial (LCX) cables1,2) as wireless antennas, wehave successfully established a cost-eﬃcient and easyto-maintain Wi-Fi environment.
An LCX cable is a type of antenna in which slots
are placed in the outer conductor of a coaxial cable
to enable wireless communication. Figure 1 shows thestructure of an LCX cable. We adopted LCX cables(Proterial Ltd. F-8D-LCX) that can be extended toa maximum cable length of 100 m and are compatible
with the 2.4 and 5 GHz Wi-Fi bands. A diagram of thewiring in the B1F and B3F measurement rooms of theRIBF building is shown in Fig. 2. Boxes labeled withAP, circles, and bold lines are the access point, experimental room, and LCX cables, respectively. An HPE
Aruba AP-504 access point, which is compliant withthe 2.4 and 5 GHz Wi-Fi bands, was adopted. TwoLCX cables are connected to each access point, andᲴᯈ

'36㺃(36APFig. 2. Wiring diagram for the B1F and B3F measurement
rooms in the RIBF building.

two access points were installed on each ﬂoor. Eight
LCX cables (15, 38, 40, 50, 50, 60, 67, and 80 m)
were used, and the total length was 400 m. Cables
were routed along walls or cable racks on the ceiling.
As shown in Fig. 2, four access points and eight LCX
cables were suﬃcient to cover all the B1F and B3F
measurement rooms.
The Wi-Fi signal strength is generally consideredgood if it is above −50 dBm. Near the access point, theWi-Fi signal strength was approximately −40 dBm forboth the 2.4 and 5 GHz bands. At a distance of 80 mfrom the access point, the signal strength was about−70 dBm for the 2.4 GHz band and less than −90 dBm
for the 5 GHz band. However network communication
was possible with the 2.4 GHz Wi-Fi band.
These results show that the Wi-Fi environment using LCX cables is eﬀective in an experimental areasuch as the RIBF, where several measurement rooms
are separately located. In the future, we plan to construct a Wi-Fi environment with LCX cables in themeasurement rooms of the Nishina Building.
References

Insulator

1) https://ww.hcnet.co.jp/products/wireless/lcx/lcx.
html .
2) T. Igarashi et al., in Computers in Railways IX, edited
by J. Allan et al., (WIT Press, 2004), p. 455.

SlotFig. 1. Structure of an LCX cable.
∗1∗2

RIKEN Nishina Center
RIKEN Information Systems Division- 120 -