Yang, Linda

Yeung, K.

English

Name not available

Mobile Information Retrieval in a Hybrid Peer-to-Peer 
Environment 
Kam Fung Yeung, Yanyan Yang 
Dept. of Electronic and Computer Engineering, University of Portsmouth 
Anglesea Building, Anglesea Road, 
Portsmouth, Hampshire, PO1 3DJ, United Kingdom 
+44 2392 84 2543 
{kam.yeung, linda.yang}@port.ac.uk
ABSTRACT 
The proliferation of wireless and mobile devices has created a 
large demand for mobile information content as well as effective 
mobile information retrieval. In this paper, we present JHPeer, a 
software framework for mobile information retrieval in hybrid 
peer to peer (P2P) networks. JHPeer incorporates context engine 
to fit on mobile devices to enable context-based personal 
information retrieval. A prototype system has been developed 
based on JHPeer framework for retrieving, indexing and sharing 
user information on mobile devices in P2P environment. 
Categories and Subject Descriptors 
C.2.4 [Computer-Communication Networks]: Distributed 
Systems - distributed applications; H.4.3 [Information System 
Applications]: Communications Applications - information 
browsers; H.5.3 [Information Interfaces and Presentation]: 
Group and Organization Interfaces - collaborative computing 
General Terms 
Management, Documentation, Performance, Design, 
Experimentation, Human Factors, Standardization. 
Keywords 
Peer-to-Peer, Hybrid Framework, JXTA, Context-awareness, 
Information Retrieval 
1. INTRODUCTION 
Traditional information retrieval techniques were developed to 
achieve efficient document retrieval over a collection of 
documents. These later on, started to focus towards more hybrid 
and distributed information systems such as the World Wide Web. 
Contemporary web search engines and web directories target 
desktop users by returning them documents based on user queries. 
Similar with accessing to an existing www contents isn’t just 
enough for a mobile user. With the realization of pervasive 
computing technologies, user surrounding is becoming more and 
more information rich. In such an environment, a typical mobile 
user will come across different information sources while being 
on the move. The nomadic nature of user itself puts a lot of 
constraints and brings about a lot of dynamics to user’s context. 
Mobile users’ information needs change as they change their 
location as well as other contextual attributes such as task, 
emotional or environmental context. The centralized system 
cannot satisfy the mobile user's demand for effective information 
retrieval and sharing due to the rapid growing of mobile users 
seeking for dynamic information. Being on the move, the 
organization of communication network will be highly dynamic 
for both the user and the information. 
As the advent of wireless technologies and constant development 
of mobile devices, the ability of sharing information through a 
P2P service on mobile devices has become a promising 
alternative to centralized approach for large-scale data retrieval 
and sharing. A range of wireless network technologies such as 
Bluetooth, Wi-Fi (Wireless Fidelity), 3G cellular network or 
WiMAX (Worldwide Interoperability for Microwave Access) that 
fitted on ubiquitous mobile devices are common. These mobile 
networks allow mobile users to access for information anytime, 
anywhere and provide users with satisfactory average bandwidth 
for P2P communication rather just browsing web or email reading. 
Additionally, mobile network operators also have acknowledged 
the ubiquitous mobile services that are the obvious trend. They 
are offering their customers unlimited Internet access with a 
lowered price [2]. This leads to a growing importance of 
information services on the move. However the quality and 
quantity of in-time personal information services available for 
mobile users still lag behind.  
In this paper we present a software framework, called JHPeer 
(JXTA [1] based Hybrid Peer to Peer), for context based mobile 
information retrieval and sharing in hybrid peer to peer (P2P) 
networks. JHPeer is a generic framework which enables the 
development of software applications for mobile environment 
such as Mobile Map, Mobile Blog, Tourism, Social Collaboration 
and personalized mobile information retrieval. This paper shows 
how the functionality required for personal mobile information 
sharing applications can be achieved through a set of application 
components in a simple way, and how to provide in-time context-
sensitive information services to mobile users in a in P2P fashion. 
A prototype system has been built based on the proposed 
framework. 
The rest of this paper is organized as follows. In section 2, we 
briefly review related work. Section 3 describes JXTA based 
Hybrid Peer to Peer (JHPeer) framework and introduce the main 
considerations of the design. Section 4 explains how we model 
the context. Section 5 discusses the application scenarios. In 
section 6, we report on the implementation status of our system. 
We conclude in section 7. 
Permission to make digital or hard copies of all or part of this work for 
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Mobility 2009, Sep 2-4, Nice, France Copyright © 2009  
ACM 978-1-60558-536-9/00/0009……$5.00 
2. RELATED WORK 
Several frameworks [3, 4, 7, 8] have been previously proposed to 
implement context-aware application. CASS [3] is a server-based 
middleware that facilitates context-aware application on mobile 
devices. Because of the server-based approach, it suffers from 
central server failure and memory/processor constraints. SOCAM 
[4] is ontology-based context-aware service focused on a smart 
space domain. It uses OWL to resolve the issues of context 
modeling and context reasoning. However, it is implemented in 
Java RMI technology and is not suitable for large-scale network. 
CoBrA [7] is an agent-based framework that deploys intelligent 
context broker to receive, integrate and share the contexts. CMF 
[8] is designed for context management for processing and 
exchanging context information in mobile environment. It aims to 
operate in pure peer-to-peer framework. 
Previous approaches adopt semantic technology for developing 
context-aware application. However, most of them either rely on 
centralized service or operate on a pure peer to peer fashion. The 
former approach suffers from a single point of failure and has 
limited scalability while the latter approach may overload the 
network and is less efficient. JHPeer uses hybrid approach with 
multiple super peers to address these problems. JHPeer 
incorporates information retrieval engine which uses context-
awareness for effective information retrieval in such environment.  
3. THE JHPEER FRAMEWORK 
Figure 1 presents the hybrid P2P framework of JHPeer. 
JHPeer framework is designed to enable the development of 
software applications for mobile environments. The framework 
follows most of desktop based peer to peer systems in that each 
node is equal and performs both client and server functionality. It 
consists of 2 types of Peers – Super Peer and Mobile Peer. The 
existence of the super peer creates a slightly different framework 
from the standard P2P framework in which no central server 
exists. 
Both Super Peer and Mobile Peer incorporate an information 
processing engine which supports the filtering of content with 
respecting to user preference and context information, providing 
effective information retrieval in a p2p fashion. The difference 
between super peers and mobile peers are that super peers are 
responsible for creating and monitoring the overlay network and 
providing searching and directory services to other super peers 
and mobile peers. Super peers also provide message propagation 
and knowledge caching. Mobile peers dynamically join to the 
networked community and provide information for sharing, and 
allow context based retrieval. The functions of each component 
are described as follow: 
Query Processor – handle and process queries, allow context 
based retrieval. 
Context Processor -manage and share context information in the 
Peer Group network. 
Indexing Components - organize information into index file for 
fast searching and save temporary information in the database.  
Network Monitor - monitor the peer network and check for 
online peers. 
Application components - are services components deployed in 
the system for providing functionality to users. 
4. CONTEXT MODELING 
A Context is the information about a person’s proximate 
environment. Pervasive System will use the context information 
on decision and anticipating user needs. Proactive information 
services which automatically retrieve relevant information for 
user would help to meet user expectation transparently. Context 
information can be divided into static and dynamic context. Static 
Context refers to context that is seldom changed during service 
usage such as personal calendar/schedule, address book, contact 
list, to-do list, user profile and hardware profile. Dynamic Context 
is the frequency changes information and usually is the 
information that is gathered by sensors like location, temperature, 
time, speed and emotion. 
In order to enable context-aware computing, contextual 
information needs to be modeled and allows application to 
interpret relevant context. Key-value model is used to tag context 
Figure 1. JHPeer Framework 
data inside a XML message for the purpose of distributing context 
resource among Peers. Each piece of contextual information is 
tagged inside the Tag <jhpeer:Context> ... </jhpeer:Context> in 
the XML Message. For increasing the flexibly of our framework, 
the content of context information could be constructed from 
structured XML Schema, Resource Description Language (RDF) 
[5] or Web Ontology Language [6] depending on the requirement 
of the service. 
Examples for location-aware services such as various social 
services allow locating your friend on the maps and finding the 
distance. These gather position information from various sensors 
includes GPS, AGPS, WiFi, RFID and mobile phone tower 
(CellID). This type of services will require Location-ontology 
based XML for communication. Several models could be used 
such as RDF, KML [9] or custom XML Schema. For RDF, 
<geo:lat> and <geo:long> could represent the global position. For 
KML, it is designed for expressing geographic annotation which 
contains additional information like place mark description, icon, 
style...etc. For custom XML, context attributes need to be defined. 
A couple of attributes include name, position, address are required. 
Additionally, attributes like timestamp, gathered sources, 
accuracy will benefit the computation. 
5. JHPEER APPLICATIONS 
Several potential applications may be integrated into JHPeer 
System as follows. 
5.1 Tourism 
Tourism service could enhance tourist experiences, even locals. 
Once a user starts this application, system would provide local 
information depending on the geographical position. For example, 
a mobile Wi-Fi user accesses Portsmouth. The application would 
acknowledge the location where the user is via GPS/AGPS and 
offers some useful recommendation, e.g. address of the nearest 
Holiday Inn, special event of the popular pub and the sale 
information in nearby shopping centre. If the user selects the 
address of the nearest Holiday Inn, the system will provide further 
personal information, like the directions to Holiday Inn and price 
of the hotel for different service. 
5.2 Mobile News 
News Service could benefit mobile user by automatic publishing 
up-to-date relevant news and alerting user with interested topics 
using user's preference and contexts. Imagining that you arrive a 
city, the system will report the current local event, traffic 
information and weather situation. All these resource will show to 
the user without formulating any query. It will just be achieved by 
locating the user position. The most benefit of this service is that 
the user could make the decision timely by updating the news at 
the first time when it occurs.  
5.3 Mobile Discussion Board 
Discussion board could be applied in several areas, e.g. 
communicating the quality of one product or the situation of on-
going football game. Mobile discussion broad provides an 
information sharing platform to fulfill the demands of user to the 
fullest extent. The other good example is about the stock 
discussion platform. Because of the attribute of the stock market, 
it will produce plenty of data, and the stockholders need to 
exchange the information as fast as possible. Offering a mobile 
discussion broad is desirable for the specific market environment.  
5.4 Mobile Blog 
Nowadays, creating users’ own blog and expressing themselves 
about anything have become the habit of people. It is the 
approach that allows people to record the current feeling. 
However, since the limitation of desktop blog, blog likes an 
online dairy than an emotion note. Mobile blog lets user to share 
the moment which is happened. Also, in our system, people could 
read the mobile blog which is posted by the user who is in the 
same location. It will facilitate the communication between those 
mobile users the people next to you and share the feeling for the 
same event.  
6. STATUS OF IMPLEMENTATION 
We have prototyped JHPeer using Java and deployed it on a small 
network of mobile devices. Figure 2 shows a simple prototype 
that implement on HTC Touch emulators (Windows Mobile). It 
allows mobile user to search nearby resources and friends 
locations via published context information, which pushes 
interesting information to users based on user’s context 
information rather than to require the users to search the 
information they need. Map/Friend Service enables user to find 
his friends nearby. Friend could be added and located by 
searching through the contact list in the mobile phone or manual 
search by user through email. 
 
Figure 2. Prototype Screen Captures 
Different mobile users may be interested in different information 
services. We use departmental forum as an example service. As a 
scenario, Lee is a third year student. He is interested in all posts in 
his current units: B305, B353. He is also interested in the topics 
of housing and exam since the exam is coming and he needs to 
move out from the hall of resident soon. With the support of 
Super Peer that will automatically push the most relevant topics to 
his mobile devices that he may be interested in. So he won’t miss 
any important posts. He is able to add or remove any interest in 
the user profile through the Setting Interface. 
We carried out some initial experiments in order to evaluate the 
performance of the developed prototype. We publish around 
15,000 advertisements to the Peer Group in our test. These 
advertisements include user preferences, user contexts and the 
content of forum discussion. The average time taken for results to 
be received after a query was broadcasted was 800 milliseconds 
(ms). The value is acceptable for the prototype system to be used 
in future user experiments. Table 1 shows the detail of cost for 
processing a forum request. The mobile device took about 2 ms to 
generate the query XML message and passed it to JXTA Pipe 
Service Queue for transmission. It took about 50 ms to pass to 
other peer through Local Network, while the time is depended on 
network condition and sizes. The Forum Service in Super Peer 
only needed around 20 ms to process and response the query. 
However, the result was usually a list of Thread data that required 
more time to send back to mobile peer. Mobile peer would handle 
the message and parser the XML to runtime variable. This process 
is various due to the size of message. 
Table 1. Transmission Cost 
Task Simulated (ms) 
Mobile Peer Message formulation 2 
Message in-Queue 10 
Transmission to Super Peer 50~100 
Super Peer Service Process Time ~20 
Transmission to Mobile Peer 100~500 
Mobile Peer JXTA Message handle time 100~400 
Mobile Service Message parser time 2 ~ 14 
7. CONCLUSION 
In this paper, we describe a JXTA based Hybrid Peer to Peer 
context-aware system for mobile information service. The JHPeer 
system allows distributed access, concurrent querying and parallel 
computing for mobile information retrieval system over a large 
scale of mobile network. JHPeer deploys a Query and Context 
Processor to process context information and provides in time and 
personal information for mobile users. The JHPeer system can 
grow while adding new super peers and mobile peers.  
Previous research has been focused on pure P2P technologies or 
relied on a single centralized directory service. What we are doing 
is to build the foundation of peer to peer technology and JXTA 
platform for context based searching and sharing of mobile data, 
and put this work into engineering practices. Our investigation is 
just at the beginning, and far from accomplishment. However, we 
believe that autonomous and scalable environment is necessary 
for efficient information sharing in a mobile context. In the near 
future, we will try to build such an environment for mobile users 
and investigate the cost, performance and energy consumption of 
this system.  
We are currently working on implementation of context based 
information retrieval, a better messaging delivery mechanism 
over JXTA network to overcome potential disconnection of 
mobile wireless devices, and implementation of network 
connection APIs over Wi-Fi, Bluetooth and cellular network 
access point. 
8. REFERENCES 
[1] JXTA. 2009. JXTA Community Projects. 
https://jxta.dev.java.net/.  
[2] Richardson, T. 2006. T-Mobile to make mobile net service 
'unlimited'. The Register.  
http://www.theregister.co.uk/2006/03/24/t_mobile_unlimited. 
[3] Fahy, P. and Clarke, S. 2004. CASS – a middleware for 
mobile context-aware applications. In Workshop on Context 
Awareness, MobiSys 2004. 
[4] GU, T., Pung, H. K. and Zhang, D. Q. 2005. A service-
oriented middleware for building context-aware services. 
Journal of Network and Computer Applications, Vol 28 issue 
1, 2005, pp. 1 – 18. 
[5] Herman, I. Swick, R. and Brickley, D., 2004. Resource 
Description Framework (RDF)/W3C Semantic Web Activity. 
http://www.w3.org/RDF/ 
[6] Herman, I. 2004. Web Ontology Language OWL/W3C 
Semantic Web Activity. http://www.w3.org/2004/OWL/. 
[7] Chen, H., Finin, T. and Joshi, A. 2003. An ontology for 
context-aware pervasive computing environments. The 
Knowledge Engineering Review (2003), 18, Cambridge 
University Press, pp. 197-207. 
[8] Van Kranenburg, H., Bargh, M. S., lacob, S. and Peddemors, 
A. 2006. A Context Management Framework for Supporting 
Context-Aware Distributed Applications. IEEE 
Communications Magazine, vol 44, issue 8, pp 67-74. 
[9] KML. 2009 Keyhole Markup Language. 
http://www.opengeospatial.org/standards/kml/ 
 


Mobile information retrieval in a hybrid peer-to-peer environment

Portsmouth University Research Portal (Pure)

A Context Management Framework for Supporting Context-Aware Distributed Applications.

A serviceoriented middleware for building context-aware services.

An ontology for context-aware pervasive computing environments. The Knowledge Engineering Review

CASS – a middleware for mobile context-aware applications.

Keyhole Markup Language.

Resource Description Framework (RDF)/W3C Semantic Web Activity.

T-Mobile to make mobile net service 'unlimited'. The Register.

Web Ontology Language OWL/W3C Semantic Web Activity.

https://researchportal.port.ac.uk/portal/services/downloadRegister/99986/Y_Yang_Mobile_IR.pdf

Mobile information retrieval in a hybrid peer-to-peer environment

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