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Enomoto, M., Shibata, N., Yasumoto, K., Ito, M. and Higashino, T.: A demand-oriented information retrieval method on MANET, International Workshop on Future Mobile and Ubiquitous Information Technologies (FMUIT'06). http://ito-lab.naist.jp/themes/pdffiles/060510.makoto-e.fmuit06.pdf In urban areas including shopping malls and stations with many people, it is important to utilize various information which those people have obtained. In this paper, we propose a method for information registration and retrieval in MANET which achieves small communication cost and short response time. In our method, we divide the whole application field into multiple sub-areas and classify records into several categories so that mobile terminals in an area holds records with a category. Each area is associated with a category so that the number of queries for the category becomes the largest in the area. Thus, mobile users search records with a certain category by sending a query to nodes in the particular area using existing protocol such as LBM (Location-Based Multicast). Through simulations supposing actual urban area near Osaka station, we have confirmed that our method achieves practical communication cost and performance for information retrieval in MANET.
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A Demand-Oriented Information Retrieval Method on MANET
Makoto ENOMOTO ， Naoki SHIBATA† ， Keiichi YASUMOTO ， Minoru ITO ， Teruo HIGASHINO †
†
Graduate School of Information Science,
Nara Institute of Science and Technology†Department of Information Processing and Management,
Shiga University† † Graduate School of Information Science and Technology,
Osaka University
Presenter: Makoto ENOMOTO
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BackgroundMobile terminals’ processing power is rapidly increasing.These devices now have wireless communication capabilities such as IEEE 802.11 and Bluetooth.
It is desired to utilize MANET to allow people to exchange various information which those people have obtained as if MANET is a database system.
It is desired to utilize MANET to allow people to exchange various information which those people have obtained as if MANET is a database system.
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Purpose of the StudyEvaluated Criteria short average response time(from sending a query to receiving a first reply) small traffic amount
Policy Maintenance free, stateless routing no concentration of load on particular terminals
This study aims to realize an efficient method which satisfies these criteria.
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Contents of Study
1. User’s Perspective
2. Assumption and Problem Definition
3. Basic Ideas
4. Detailed Proposed Method
5. Experiment and Evaluation
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User’s perspective （ when register ）Data item(hereafter record):
combination of
ID ， timestamp ， location ， main data(text ， images),keyword, [prices ，… ]
Record example: (0,19:00,135.29-34.41,“Yamato”,“Japanese Style Restaurant, Happy Hour”,-)
Data item(hereafter record):
combination of
ID ， timestamp ， location ， main data(text ， images),keyword, [prices ，… ]
Record example: (0,19:00,135.29-34.41,“Yamato”,“Japanese Style Restaurant, Happy Hour”,-)
Registeringrecord
Preservingrecord
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User’s perspective （ when search ）
Searching Example： Time ＝ 19:00-20:00,
Location ＝ less than 500m from Osaka Station,
Category ＝ Japanese Style Restaurant
Searching Example： Time ＝ 19:00-20:00,
Location ＝ less than 500m from Osaka Station,
Category ＝ Japanese Style Restaurant
Searchingrecord
Preserved record
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Mobile Terminal （ laptop PC,PDA,cell phone ） has wireless communication capabilities. has some memories. is carried by a person and therefore each node moves. knows its geographical position by GPS. has a unique ID number.
The geographical region where the proposed method is operated is predefined.
Assumption
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Problem Definition
available restaurant
Train delay info
congestion at event site
Shopping info,
happy hour
Assume that query frequency varies widely according to location （ station, event site, …） category （ traffic， shopping, …）
Find the distribution of records that minimizes the average response time
Assume that query frequency varies widely according to location （ station, event site, …） category （ traffic， shopping, …）
Find the distribution of records that minimizes the average response time
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Basic IdeasIf all of registered records are replicated in all nodes,
the average response time becomes minimum.
replication cost also becomes high
In the proposed method, we replicate records only in the nodes in the area with the largest demand
Approach ：
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Proposed MethodSTEP1: Classify records into classes
Record: ID ， timestamp ， location ， main data(text ， images),keyword,
[prices ，… ]
All records are divided into multiple sets
Class1: On SaleClass1: On Sale
Class2: EventClass2: Event
Class3: Train DelayClass3: Train Delay
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Proposed MethodSTEP2:whole application field is divided into sub-regions (hereafter areas)
A B C
1
2
3
A1 B1
A2
A3
B2
B3
C1
C2
C3
FMUIT 12Demand ; measured by the count of query sent to the area
Class Count
On Sale 23
Event 11
Train 10
Class Count
On Sale 4
Event 7
Train 17
Class Count
On Sale 70
Event 86
Train 21
Class Count
On Sale 5
Event 11
Train 1
Class Count
On Sale 8
Event 10
Train 3
Class Count
On Sale 54
Event 119
Train 32
Class Count
On Sale 32
Event 11
Train 16
Class Count
On Sale 66
Event 11
Train 9
Class Count
On Sale 68
Event 150
Train 23
Proposed MethodSTEP3:All nodes count the number of matched queries for each class
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Proposed MethodSTEP4:Find the most demanding area
Class Count Area
On Sale 8 A1
Event 10 A1
Train 3 A1
A1’squery count table Class Count Area
On Sale 8 A1
Event 11 A2
Train 3 A1Class Count Area
On Sale 5 A2
Event 11 A2
Train 1 A2
(i) Area ‘A1’ flood the its query count table
(ii) Area ‘A2’ receive the table
(iii) Area ‘A2’ compares entries of the table and its own table, and updates the table so that each table entry has higher value between two tables and flood again
A2’squery count table
A1 B1 C1
A2 B2 C2
A3 B3 C3
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Proposed MethodSTEP5:Replicate records in the most demanding area
A B C
1
2
3
Data sending node
Example
1.registering a record which ClassID = 3
2.most demanding area of the Class is ‘C1’
3.Sending registering message to ‘C1’
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Proposed MethodSTEP6:Send query to the most demanding area
A B C
1
2
3
Query sending node
Example
A node in ‘A2’ sends a query to ‘C1’
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Experiment and Evaluation
The target geographical region 500m × 500m region around Osaka
Station
0 1
2
3
45
67
89 10 11
1213
14 15 16 17 18
1920 21 22
23
24
25
26
27
28
29
30
31
32
3334
Distribution of Nodes1.Nodes are placed on the roads according to the actual observed density.
2.For simplicity, nodes are assumed not to move.
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Experiment - implemention
ProtocolsFlooding
used when sending a query or a record to nodes in a particular area
used when a message is sent to the entire ad-hoc network
Location-Based Multicast (LBM)
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Experimental Result – Average Response Time
0
20
40
60
80
100
120
140
0 200 400 600 800 1000
Number of Nodes
Ave
rage
Res
pons
e T
ime
Flooding LeastDemanding MostDemanding
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Experimental Result – Number of Messages
0
50000
100000
150000
200000
250000
0 200 400 600 800 1000
Number of Nodes
Num
ber
of a
ll m
essa
ges
Flooding LeastDemanding MostDemanding
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Experimental Result – Reply Loss
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 200 400 600 800 1000
Number of Nodes
Rep
ly L
oss
Flooding LeastDemanding MostDemanding
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ConclusionsWe have proposed an information retrieval method on MANET that achieves low communication traffic and short response time ．Simulation using actual geographical information with measured pedestrian density in Osaka city.
Future WorksEstimating the overhead of control messages for finding the most demanding areas and record replication costSimulations under the conditions where pedestrians move along the roads with realistic pedestrian density on each road
