Last One Mile Connectity at the Time of Disaster
Satellite network system is a promising solution that can provide the Internet access to disaster areas.
However, it is impossible to deploy the ground stations to all disaster areas in terms of cost and thetechnical limitations. Therefore, extending the limited Internet connections to the disaster areas is aneffective way to expand the network connectivity.
For the purpose, we have performed two experiments. One is an experiment using a satellite circuit and a wirelessmultipath network for DMAT (Disaster Medical Assistance Team) in medical disaster prevention drills conducted inWakayama on July 29, and the other is an experiment of wireless relay using drone.

Abstract

Case1: An Experiment of Wireless Multipath Network Effectiveness

Satellitefrom Land to a Ship for an SCU Activity Support NetworkEarthStationLAN

Wireless LAN
Car Mounted VSAT
Ad-hoc Satellite Internet
Communication SystemLAN

DMAT Headquarters(inboard)

Internet
EMIS
Emergency Medical
Information System

2.4GHz Pattern 1

JRL820AP2

Performance evaluation of the equipmentusing the 2.4GHz band that is easy to install at thetime of disasters

5.6GHz Pattern 2

DMAT : Disaster Medical
Assistance TeamiPASOLINK

JRL820AP2

As the 5.6 GHz band is also used for theweather radars, it needs to be verified whether it
is available without any trouble on the ship

AX2530-08P

iPASOLINKiPASOLINK60GHz

iPASOLINK

AX2530-08P

Pattern 3

Link
Aggregation

Link
Aggregation

25GHz

Utilization of the link aggregation
and VLAN function of AX2530-08P
manufactured by ALAXALASDF Ship of Osumi

NTG2501

Performance evaluation using one virtual circuit
aggregating multiple wireless links so that it canstably maintain the link on the rocking ship on the sea

Small transportable VSAT*with autonomy UAT* system
VSAT : Very Small Aperture Terminal
UAT : Uplink Access Test

NTG2501

200 ～ 400m

SDF Ship of Osumi

Land

System configuration diagram▶ The 5.6 GHz band is not available on the ships

Result▶ Link aggregation (LACP) is effective to improve availability▶ The bandwidth of the satellite line is the bottleneck rather than the last one mile networkLandCase2: An Experiment of a Drone Wireless Network Effectiveness from Land to a Ship
for an Staging Care Unit(SCU) Activity Support Network at the Time of Disaster
Implemented October 17, 2018Drone
DJI S800

Satellite

Height 20m

Point A (ship)Mesh Network
2.4GHz

WiFi Network for Client
5.6GHz

Point B (Land)

EarthStation

Wireless AP
JRC JRL820AP2Internet
AlaxalaIperf client

AX2130S-24P

Ad-hoc Satellite Internet
Communication System

PoE power supply
capacity：370W
Iperf client

80m

EMIS
Emergency Medical
Information System

Iperf server tcpdump

Results and Consideration
Iperf Client → Server Data Transfer (TCP)

Iperf Client → Server Data Transfer (UDP)

2Throughput : MAX 1.8Mbps
Many retransmissions
Delay is 50msec

Throughput : MAX 1.2Mbps
NO retransmission because of UDP
Delay is 50msec

There is no problem as throughput and delay requiredat the time of disaster.

There is no problem as throughput and delay requiredat the time of disaster.

However, Access to EMIS may be affected, as there aremany TCP retransmissions.

There is no problem for audio communication andTV conference.

▶ Wireless relay using drones expands the range of use of satellite link.

Conclusion▶ There is possibility of Web access failure because of TCP packet retransmission.
▶ No problem for Audio and Vide Communication

FutureChallenges▶ Issues for TCP Packet retransmission▶ Experiment using drone at DMAT training in the Kyushu area on November 10 is under review

NAIST: http://www.naist.jp