design and analysis of a mobile file sharing system for opportunistic networks

7/29/2019 Design and Analysis of a Mobile File Sharing System for Opportunistic Networks

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Design and Analysis of a Mobile

File Sharing

BY:

SADIQUE NAYEEM(PONDICHERRY UNIVERSITY)


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Outline

Design and analyze a mobile file sharing systemover opportunistic networks using Bluetooth

technology.

To enable a mobile device to download desired filesfrom available devices in its neighborhood and also

allow its files to be disseminated to the network

with the facilitation of opportunistic contacts.

The key challenges to be address are systemautomation and file sharing efficiency.


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Opportunistic networks

Now a days many devices can support spontaneous

interaction among mobile users through wireless

links, such as Bluetooth and Wi-Fi. The resulted

network is often referred as an opportunisticnetwork(Oppnet). In these networks, contacts

among users are usually opportunistic and

connections among devices are intermittent.


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Basic

operational

phases in an

Oppnet.


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File Sharing

File sharing scenario of the system can be described as follows: Mobile devices search for available devices in their

neighborhoods.

Request for file sharing services

Establish the connection

At the same time, these mobile devices serve as service

providers and respond to requests sent from their neighbors

The Transaction can be

File Pulling

File Pushing


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File Pulling & File Pushing

File pulling is to download files from neighbors.

File pushing is to distribute files(Ex- Conference)

There are two different pairs of roles in our file

sharing system:

(puller, pullee)

(pusher, pushee)


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Puller is the one who requests for pulling service and

desires to download files from the service provider calledpullee.

Pusher is the one who requests for pushing services and

wants to distribute its owned files to the service provider

named pushee.

ROLES RELATIONSHIP


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File Sharing

Pusher(Responder)

Pullee (Responder)

Pushee (Requester)

Puller (Requester)

Download


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Mobile File Sharing

System for Opportunistic Networks

The mobile file sharing system includes three

main components:

Connectivity mechanism

Download control and

Break handling.


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System Overview


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Connectivity mechanism

The connectivity mechanism is designed to

handle connection for a mobile device for its

diverse roles.

Device discovery

Neighbor selection

Connection establishment.


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Connectivity mechanism - Device discovery

Bluetooth technology for short range communication

which scans for available devices in the neighborhood

periodically.

Experimentally the device discover neighbors within 17

seconds if there exists at least one in the neighborhood.


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Connectivity mechanism -Neighbor selection

Once available neighbors are discovered

The neighbor selection strategy is applied for file puller and

pusher to choose a neighbor.

The file puller maintains a list locally which traces all themobile devices that have unfinished file transferring in

their last connections with the puller.

If such neighbor is found then file transferring completes

successfully . Else the file puller chooses the connection candidate from

all available neighbors randomly.


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Connectivity mechanism - Neighbor selection

A file pusher also maintains a list locally which

records all the mobile devices which it has pushed

its files.

If discovered neighbors exist in the list, the filepusher will avoid selecting them as connection

candidate, since pusher does not want to push files

to the same device repeatedly.

Then the file pusher chooses the connection

candidate randomly from all the other available

ones.


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Connectivity mechanism - Connection Establishment 1

The system involves two pairs of roles i.e (puller, pullee) and

(pusher, pushee) and connection only occurs between

puller and pullee or pusher and pushee respectively.

For the pair of file puller and pullee, search criterion is

used to announce its file requirement including file types it

requests. ie. jpeg, .mp3 etc.

search criterion is send to file pullee

file pullee accepts the service request if at least one file in

its possession meets the criterion and sends backacceptance notice with its provided files information.

After receiving the acceptance notice from file pullee,the

connection b/w puller and pullee is established

successfully.


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Connectivity mechanism - Connection Establishment - 2

For file pusher and pushee, the pushed file information is

used by the pusher to announce files that it desires to

distribute to the network.

The file pusher sends out pushing request along with the

pushed file information.

A selected neighbor acting as file pushee accepts the

service request and sends back an acceptance notice.

The connection is announced to be establishedsuccessfully.


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ROLES AND FILE INFORMATION LISTS

Each mobile device is capable of serving up to 4 types ofroles whose connection processes for file puller, pullee,

pusher and pushee can be described by the following four

Algorithm.


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Download Control

After the connection established, download control

handles file transferring process. The challenge of

download control is

To reduce file transferring duration

Improve file sharing efficiency

As puller and pushee are the ones that download files

from pullee and pusher, they can customize their

download sequences with the help of prioritizing

sequence of these files.


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PRIORITIZED DOWNLOAD SEQUENCE


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Piece Information

The puller or pushee breaks all the prioritized files that are

about to be downloaded into certain size of pieces.

Piece information is recorded in a meta file.

Using file piece has two advantages. Firstly, it allows a file to be downloaded from multiple devices as

a device can request different pieces of a file from multiple

devices simultaneously.

Secondly, it facilitates connection break handling.

Similar to connectivity mechanism, download control

manages the downloads for the mobile device in different

roles and the download control processes can be described

by the following Algorithm.


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Connection Break Handling

Due to device mobility in opportunistic networks,

opportunistic contacts occur and disappear

frequently. As a result the transfer of data is not

completed successfully. Here the break handlerworks which store all existing pieces of unfinished

files temporarily and request for the rest pieces

when the connection is rebuilt.

EVALUATION I


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EVALUATION - I

The file transferring data rate limiting the peer number to 4

will maximize the data rate


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EVALUATION - II

The time taken to merge pieces into a file is minimal when the

file piece size is 100 KB.

EVALUATION - III


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EVALUATION III

File compression is applied on the file provider to reduce file size,

thereby reducing the file transferring duration.

The time taken to download files can be reduced significantly for somefile types, such as .txt and .bmp.


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EVALUATION - IV

Finally the whole system efficiency is measured consideringthe time taken not only for the file transferring but also the

preparation operations before the transferring and the merging

afterwards.

Preparation operations includes

discovering neighbors

establishing connection with the selected neighbor

Initiation work in download control.

EVALUATION - V


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EVALUATION V

The time taken to transfer files and merge pieces into files are

directly related to the file size

CONCLUSION


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CONCLUSION

The mobile file sharing system proposed in this paper provides

an efficient solution for mobile devices in opportunisticnetworks to acquire interested files from neighbors and also

distribute files to the network. It is implemented on HP iPAQ

910 smart phones equipped with Bluetooth interfaces. It

allows one mobile device to download or upload files from or

to multiple neighbors and achieves up to 417 KB per second

data rate for file transferring. It is indicated that limiting the

peer number to 4 maximizes the data rate and enhances the

system efficiency. The use of file piece enables connection

break handling. It is clearly shown that file piece with 100 KBsize can minimize the extra time cost according to our

experiment results.


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Thank you!

design and analysis of a mobile file sharing system for opportunistic networks

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