Trekking Navigation System using Opportunistic Communication

Yasuhiko Kitamura, Shunsuke Nosaka, Hirofumi Kishino and Yui Okuda

Department of Informatics, Kwansei Gakuin University, Sanda, Hyogo, Japan

Keywords:

Trekking Navigation System, Opportunistic Communication, Location Estimation.

Abstract:

Mountain climbing or trekking becomes popular in Japan recently. Unfortunately the more climbers go to

mountains, the more get lost. Handy GPS’s are a well-known tool to navigate climbers in the mountain area

by displaying their location on a digital map. They are useful to know the current location, but not suitable to

call an emergency help. Cell phones are useful to call a help, but they work only in the city area accessible

to mobile phone networks. They seldom get access to them in the mountain area. This paper proposes a

new trekking navigation system, which consists of mobile terminals and a server, that works even in the poor

communication environment where the Internet access is often disrupted such as in the mountain area. The

terminals can navigate climbers even when the Internet access is unavailable. When they can get access to the

server, they send the walking trajectory of the climbers, so the rescue party can locate the climbers in need.

They can also exchange the walking trajectory with each other by utilizing opportunistic communication

and carry the information until they reach an area accessible to the server. This paper shows a prototype

of trekking navigation system under development and how the opportunistic communication improves the

location estimation of climbers.

1 INTRODUCTION

A multi-agent system (Weiss, 1999; Wooldridge,

2009) consists of multiple agents that collaborate with

each other to solve a problem, and most of research

works presuppose the communication environment is

stable with a few notable exceptions (Durfee et al.,

1987). When the communication environment is not

stable, the agents need more intelligence to cope with

the delay and/or lost of messages to be transmitted

among them. In this paper, we propose a trekking

navigation system, which can be viewed as a multi-

agent system situated in a poor communication envi-

ronment, because the communication environment in

the mountain area is typically unstable.

Recently the population of Japanese mountain

climbers is more than 10 million and a number of

climbers get into trouble because of rapid weather

changes, going astray, injury, deconditioning, and so

on.

Handy GPS’s are widely used among climbers as

an IT tool to locate them in the mountain. The tool

measures the latitude and longitude of the current lo-

cation by using GPS (Global Positioning System) and

displays its location on a digital map. It is useful when

a climber needs to know his/her current location but

not suitable when he/she needs to inform his/her lo-

cation to a rescue party.

Recently many of climbers go to mountains with

cell phones. They work as a tool to call an emergency

help while they can get access to mobile phone net-

works, but they do not work in the large part of the

mountain area because the access to the mobile phone

networks is frequently disrupted. Figure 1 shows a

cell phone accessibility map along a trekking route in

Mt. Mino, Osaka, Japan. The accessibility frequently

changes depending on the terrain. In this paper, we

call such a communication environmentas Poor Com-

munication Environment (PCE) (Fujihara and Miwa,

2010; Vasilakos et al., 2012) where the Internet access

is frequently disrupted.

In this paper, we propose a new trekking naviga-

tion system, consisting of terminals and a server, that

can work in PCE with the following functions.

1. When the terminal is not accessible to the server,

it works as a stand alone navigator to inform the

current location to the user and records his/her

walking trajectory.

2. When the terminal is accessible to the server, it

sends the walking trajectory record stored in it to

the server.

3. When a terminal encounters another terminal,

they exchange their walking trajectory records

427

Kitamura Y., Nosaka S., Kishino H. and Okuda Y..

Trekking Navigation System using Opportunistic Communication.

DOI: 10.5220/0004326504270430

In Proceedings of the 5th International Conference on Agents and Artiﬁcial Intelligence (ICAART-2013), pages 427-430

ISBN: 978-989-8565-38-9

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

Figure 1: A cell phone accessibility map around Mt. Mino,

Osaka, Japan on August 8th, 2012. (Red: inaccessible, Yel-

low: very weak, Light blue: weak, Green: moderate, and

Blue: good).

with each other by using the P2P communication

link (Fujihara and Miwa, 2010).

Figure 2 shows how the system works. Terminal A

(T A) in an Internet accessible area sends its walking

record to the server. It encounters Terminal B (T B)

in the mountain area where no Internet access is avail-

able and exchanges the records with T B. When T B

reaches an Internet accessible area, it sends its records

together with the ones from T A to the server. If the

climber with T A get lost in the mountain, the res-

cue party goes to ﬁnd him/her estimating his/her lo-

cation by referring to the walking records stored in

the server.

In this paper, Section 2 summarizes GPS applica-

tions for walkers and Section 3 shows a prototype of

our trekking navigation system developed as an An-

droid application and discusses how the estimation of

locating a lost climber is improved by using oppor-

tunistic communication. Section 4 summarizes this

paper with our future work.

Lost

Communication

is available.

Communication

is unavailable.

T_A and T_B

exchange their logs.

T_A sends the

log to the server.

T_B sends the

logs of A and

B to the server.

Climber A

Climber B

Server

Figure 2: Trekking navigation system in poor communica-

tion environment.

2 GPS APPLICATIONS FOR

WALKERS

Car navigation systems are a well known application

using GPS, but it can be applied for human walkers as

shown below.

Handy GPS’s. Garmin

has developed handy and

battery operated GPS’s to inform the current lo-

cation to the user for outdoor activities like moun-

tain climbing and trekking. The terminal works

ofﬂine, and digital maps have been installed to

show the location on its display without commu-

nication. The user can set the destination on the

map and the terminal navigates him/her to it. It

also shows the walking distance, average speed,

barometer, altitude, and so on. The maps can

be obsolete and the user requires to update them

manually.

Walking Navigation Systems. Walking navigation

systems are available as an application of

cell/smart phone and navigate users to a destina-

tion just like car navigation systems. After set-

ting a destination, the system shows routes de-

pending on the transportation such as train/bus,

car, or walk. It measures the current location by

using GPS, uploads the digital map around the

current location through cell phone networks, and

displays it on the screen. It navigates the user by

using speech synthesis and/or vibrations in a real-

time manner. It works online and the maps are

automatically updated to be the latest ones. It can

collaborate with other services such as shopping,

restaurant, and event recommendation systems.

http://www.garmin.co.jp/

ICAART2013-InternationalConferenceonAgentsandArtificialIntelligence

428

Real-time Locating Service. Japanese security

company Secom has commercialized a real-time

locating service to deal with social problems such

as kid napping, theft of cars and motorcycles,

wandering aged people, and so on. The service

utilizes a GPS terminal connected to a server

through cell phone networks. The user can locate

wandering people with the terminal through the

Internet. This service works only online.

Table 1 shows a comparison of GPS applications

for walkers. There are differences on how the digital

maps are stored on terminals, who are the target users,

and the quality of the communication environment.

Handy GPS’s are developed for users who enjoy

outdoor activities like mountain climbing, trekking,

and so on and are supposed to be used ofﬂine. The

digital maps have been installed manually in advance.

Handy GPS’s are stand alone systems that do not need

communication to the servers.

On the other hand, Walking Navigation Systems

suppose good communication environment and al-

ways work online. They are normally connected to

the servers, and they can download the digital maps

in need at any time.

The target users of Real-time Locating Service are

not ones who have the GPS terminal but the ones who

search for the one with the GPS terminal. The GPS

terminal does not have a display to show digital maps.

The system works in the good communication envi-

ronment because communication links between ter-

minals and servers should be stable to know the loca-

tion of the terminals.

The conventional systems mentioned above are

not suitable in PCEDHandy GPS’s caninform the cur-

rent location to the climber but they cannot inform it

to the rescue party when the climber gets lost. Walk-

ing Navigation Systems and Real-time Locating Ser-

vice suppose the good communication environment

and they cannot work properly in the PCE like the

mountain areas. We propose a new walking naviga-

tion system that navigates the user as a stand alone

system even when the Internet access is unavailable

and sends walking records to the server, when the In-

ternet access is available, to inform the location of the

climber to the rescue party in need.

It is difﬁcult to estimate the location of the climber

when the Internet access is unavailable for a long

time. As a remedy, we utilize opportunistic commu-

nication based on the P2P access between the termi-

nals. When a terminal encounters another, they ex-

change the walking records with each other. When

the terminal reaches an area where the Internet access

is available, it sends not only the walking record of

the terminal but also ones of the other terminals that

it has encountered. This leads to a better location es-

timation of the climbers.

3 TREKKING NAVIGATION

SYSTEM IN PCE

We are developing a new trekking navigation system

that works on a smartphone. It works without the In-

ternet access in PCE like the mountain area, because

digital maps have been installed in it. It measures

the latitude, the longitude, and the altitude of the cur-

rent location in a constant interval by using GPS and

displays the current location on the digital map. It

also measures the signal strength of mobile phone net-

works.

The terminal records the walking trajectory and

sends it to the server when the Internet access is avail-

able. It exchanges the record with the other terminal

through Bluetooth when it encounters the other ter-

minals. When the climber with the terminal gets lost,

the rescue party gets access to the server to estimate

the location of the climber referring to the walking

record.

We performed a simulation experiment to show

how opportunistic communication improve the trace-

ability of climbers. We model walking routes as a grid

world shown in Figure 3. Climbers repeat to walk

between S and G at a constant speed. It takes 200

steps to go to G and to return to S. When a climber

reaches a branch, he/she takes a route closer to the

destination. If there is a tie between two routes, he/she

chooses one at random. We record the history of en-

counters among climbers and calculate the traceabil-

ity of climbers depending on the number of climbers

in the area. Figure 4 shows a result of the simula-

tion. X-axis shows the location on route and Y-axis

shows the estimation of the location. Climbers start

from S(0%), go to G(50%), and return to S(100%).

“Ideal” means the estimation when the Internet access

is always available, and it is correct at every location

on the route. When we assume the Internet access is

available only at S, the estimation becomes incorrect

except at S. The difference becomes large when the

number of climbers is few.

4 SUMMARY AND FUTURE

WORK

We proposed a new trekking navigation system that

works even in the poor communication environment

where communication links are frequently disrupted.

TrekkingNavigationSystemusingOpportunisticCommunication

429

Table 1: Comparison of GPS applications for walkers.

Handy GPS Walking Navigation Systems Real-time Locating Service

Digital maps on terminal Manually stored Downloaded None

Users Terminal holders Terminal holders Searchers

Communication environment

Bad Good Good

Figure 3: The simulation model of walking routes.

100

0%(S) 25% 50%(G) 75% 100%(S)

esmaon

locaon on route

n=10

n=30

n=50

ideal

Figure 4: Result of simulation.

When the communication link is unavailable, the sys-

tem navigate the user by using GPS and digital maps

as a stand alone system and records the walking tra-

jectory in the terminal. When the terminal gets access

to communication networks, it sends the record to the

server. If the user gets lost, the rescue party can esti-

mate his/her location referring to the record stored in

the server. We show that the estimation is improved

by using opportunistic communication among the ter-

minals.

We have already developed a prototype system

with the navigation function as an Android applica-

tion and plan to install the communication function

to the server and the P2P communication function

through Bluetooth. We have showed that how oppor-

tunistic communication improve the location estima-

tion by using an schematic example, but we need to

further evaluate the effect changing parameters such

as the complexity of mountain routes, the frequency

of encounters among climbers, the signal strength in

the mountain, and so on.

From a view of the terminal autonomy, how to

conserve the battery is an important research issue.

The more frequently the opportunistic communica-

tion happens, the more the battery is consumed be-

cause the amount of data communication to exchange

walking records increases. We need to develop a

scheme to selectively exchange the records. Our

trekking navigation system can be viewed as a multi-

agent system consisting of autonomous behaviour to

navigate the user considering the battery consump-

tion and collaborative behaviour to share the walk-

ing records. How to coordinate the terminals with

a constraint of battery consumption is an interesting

research topic of multi-agent systems.

ACKNOWLEDGEMENTS

This work is partly supported by JSPS KAKENHI

Grant Number 21300057 and MEXT-Supported Pro-

gram for the Strategic Research Foundation at Private

Universities.

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