PERSONALLY CUSTOMIZABLE GROUP NAVIGATION SYSTEMUSING CELLULAR PHONES AND WIRELESS AD-HOC COMMUNICATION

Yoshitaka Nakamura, Guiquan Ren, Masatoshi Nakamura, Takaaki Umedu and Teruo HigashinoOsaka University, JAPAN

BackgroundBackground•Portable computing devices have been developed

•With GPS and Wireless Communication↓

•Some Navigation Services are provided•Personal Navigation•Location Searching for others•Map Search

•Few navigation service for Group has been proposed so far

•Example: Navigation for Group Tour

Problems of Group NavigationProblems of Group Navigation•This system needs route navigation and group management facilities

•Using unicast communication between the server and the terminal

•Separate download of same information is inefficient•Bandwidth congestion problem occurs when many terminal concentrates in a single base station

Our Group Navigation SystemOur Group Navigation SystemServerServer

SolutionSolution•Only a few terminals communicate with the server•Distribute information by wireless ad-hoc communication

→Traffic on the wireless Internet network can be decreased by sharing the information between terminals

ServerServer

Ad-hoc Communication

Navigation ServerNavigation Server Management Management ToolTool

LeaderLeaderMemberMember

Personal Navigation SystemPersonal Navigation SystemGroupGroup

GPS

Outline of Group NavigationOutline of Group Navigation•Servers and client softwere are implemented by JAVA•Personal Navigation Facility

•Navigation Server: Provides service on the Web•Management Tool: Customizes navigation data

•Group Management Facility•Leader: Connect to the Web by PHS or Mobile Phone•Member: Receive data via Leader by Wireless LAN

・ Comment・ Start　・ End

PathPath

・ Longitude・ Latitude・ Name　・ File・ Comment

PointPoint

・ Image

PicturePicture

・ Vector maps

MapMap

Search Engine○Route search○Create Contents○Create URL of Picture

Trim of mapSending Picture

Navigation ServerNavigation Server

SQL ServerSQL Server

Management ToolManagement Tool

Personal Navigation FacilityMobile TerminalsMobile Terminals

StartStart Turning PointTurning Point

EndEnd

Warning message

NavigationNavigation•Navigation Server provides Text, Map and Picture data to each member•Send warning message if some members come off from the navigation route

Wireless LANWireless LAN Construction of Navigation ScenarioConstruction of Navigation Scenario•Management Tool

•Construction of Scenario Mode•Users can add

•Point data（ Picture, Text message and Map）•Path data（ Text message and Map）•Route data（ Constructed by some paths）

•Rehearsal Mode

Rehearsal ModeRehearsal Mode•Emulate the mobility of users

•Users with mobile terminals seems to be moving on the general map

•Rehearse whether to transmit information correctly

Click

Synchronizes with the Synchronizes with the place on the mapplace on the map

Management ToolManagement Tool

Variable configuration files

Variable configuration files

Rehearsal Mode of Rehearsal Mode of Management ToolManagement Tool

MapMap

Mobile Terminal EmulatorMobile Terminal Emulator

Coordinates ⇒ longitude & latitude

•User who has the mobile terminal seems to move on the map•Mobile Terminal Emulator shows the navigation of the point

Simulation ExperimentsSimulation Experiments•Examination of GPS distribution intervals

•Short: Easy to observe member's position •Long: Member’s power consumption is decreased

•Simulation of the group mobility•Leader can catch its members continuously•Warning to member away does not become too late Using Network Simulator MobiREAL (http://www.mobireal.net)

A realistic network simulator for MANET It can simulate mobility of mobile node under realistic environment

Group Management FacilityGroup Management Facility•Not to make member get lost from group

•Each member periodically scatters the packet including GPS information•Members make the leader which receive this packet as a parent•Leader observes the member-node position and maintain the group

•Several leaders cover the entire group•Member makes one of leaders as parent•Leaders exchange the member-node list with each other, and know the position of all members•When members can communicate with two or more leaders, they can select one parent who receive service by itself

Group Construction•Participation in the group (child→parent)

•Each member periodically scatters the packet including GPS information•Leader adds received GPS information of the member to the member-node list•Leader delivers its member-node list to the member•Member confirms the addition to the group by received parent’s member-node list

•Distribution interval of GPS information packet is the trade-off of the power consumption and the group maintenance

1. Generate GPS packet

3. Add node A to the neighbor-list

4. Broadcast all member-node list

A

P

C

2. Receive the packet of membersAnd refresh nodes list

ServerServer

LeaderLeaderLeaderLeader

GroupGroup

Warning Message•If members left from it’s leader’s wireless range

•Cannot receive the navigation data and announce from the leader

•The leader discovers member (e.g. node A) with the problem from GPS information then the communication situation, and sends the warning packet•If the leader cannot send warning packet to the member directly, leader send it via another member (e.g. node B) near the member

Warning Packet

LeaderLeader

Node ANode A

Node BNode B

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

Time for catching node(s)

Rat

io o

f cau

ght

mem

ber(

%)

5s10s15s20s

GPS Distribution Interval•Time after member goes out of leader’s communication range, until is caught by a leader

•More than 10s, it takes much time until the warning packet reach the member•It cannot catch up with a speed away of the member when it takes 30s or more for catching

Simulation of the Group Mobility•Scenario

•Sightseeing of Kyoto city•# of leaders: 3, # of members: 200•The distance limit of wireless communication is 70m

•From the simulation results, we could confirm,•Member who starts coming off from the group can receive the warning packet•And the member can return to the group

Leaving out of wireless range

Leader’s wireless range

Receiving warning packet