Liao Jianxin

(State Key Lab of Network and Switch Technology, Beijing University of Posts and Telecommunications, Beijing 100876, China)

Abstract:With the technological advances and market development,telecommunications networks and the Internet are converging into one universal network;meanwhile,the services provided by these two kinds of networks are integrating.Pervasive services will meet demands and expectations from all aspects.The topic has become a favorite for research in Beyond Third Generation(B3G),Next Generation Network(NGN)and Next Generation Internet(NGI)fields.The concept of the pervasive services comes from pervasive computation and B3G.Their features include pervasiveness,mobility,transparency,QoS-guarantee,customization,adaptiveness,push,security,easiness,variety and time-to-market.3GPP,OMA and the B3G research program of the European Union(EU)have conducted a lot of research work about the different features of pervasive services.The current hot topics in the pervasive services research include context awareness and service enabling.

W ith different goals,legacy telecommunications networks and the Internet have different architectures,different operation modes and different services.However,with the technological advances and market development,the technologies for the telecommunications networks and those for the Internet have been interpenetrating each other,their operation modes are learning from each other,and the services they provide are expanding,overlapping and converging.

Therefore,the convergence of the telecommunications networks and the Internet is an expectable scenario.

Pervasive services emerged from this condition.With a goal that integrates the demands and expectations for the future services from the telecommunications,computer and Internet fields,pervasive services have features special for new-generation converged networks.

There is no unified definition for pervasive services yet;although,a lot of relevant research work has been conducted.This paper will make an overview of the origin,concept,features and development of pervasive services,and discuss their development tendency and hot research topics.

1 Concept and Features of Pervasive Services

The concept of pervasive services originated from two fields:one is the pervasive computing in the computer and Internet,and the other is the B3G system in telecommunications.

Pervasive computing(also known as ubiquitous computing)has been popular in the computer and Internet research areas.Its idea is to integrate computers seamlessly into the background to make users more aware of the computing tasks that should get concerns［1］.The study of pervasive computing involves wireless and sensor networks,smart space,wearable computing,context awareness,mobile computing and nomadic computing［2］;and it is dealing with more subjects.The annual IEEEInternational Conference on Pervasive Services(ICPS)was first held in 2004,with traditional pervasive computing subjects and new added pervasive service and application.The ICPS 2004 marked the expansion of the pervasive computing study into the service layer.The ICPS defined pervasive services as follows:“Pervasive services and computing are emerging as the next computing paradigmin which infrastructure and services are seamlessly available anywhere,anytime,and in any format.

This exciting new paradigm is the result of recent research and technological advances in wireless and sensor networks,distributed systems,mobile and agent computing,and autonomic computing and services［3］.”From this definition it can be seen that the ICPS regards pervasive services as the extension of pervasive computing into the service layer.ICPSemphasizes the importance of seamless access,and pays more attention to microscopic parts.

The B3G field studies complicated heterogeneous network environments(including 2G,3G,fixed telephone network,the Internet,WLAN and WiMAX network)in the future.The research subjects involve high-speed broadband access,automatic handoff and seamless connection,spectrum and resource management,adaptation and context awareness,and pervasive services and system［4］.The concept of pervasive services has been definitely proposed in the B3G research work.For example,the fourth technicalworkpackage(WP4)of Designing Advanced Network Interfaces for the Delivery and Administration of Location Independent,Optimized Personal Services(DAIDALOS),an Integrated Project in the thematic priority"Information Society Technologies(IST)"of EU Framework Program(FP)6 for Research and Development,aims at developing a standards-based operational platform for pervasive services.The WP4 defines［5］that“Pervasive services are a new and fast-moving field of research where the focus is on simplifying user interaction with the myriad of electronic services and technologies.Activities covered in this WPinclude generic context management infrasturctures,generic personalization infrastructure,privacy protection mechanisms using the multiple virtual identity concept,and generic service management mechanisms such as discovery and composition.”In this definition,the B3G research field understands pervasive services as a generic service environment across complicated heterogeneous networks.

There is no essential difference between these two definitions;they only describe pervasive services from different aspects and with various concerns.The B3G field is thought here to have a more complete,fuller and deeper understanding of pervasive services.In fact,B3G no longer only belongs to the telecommunications field.With the active participation of a large number of entities from the computer and Internet field and the use of numerous relevant technologies,the B3G research work has a broad scope,covering all the layers from network access to service provisioning.The B3G research subjects include most parts in the pervasive computing research.Therefore,B3G system has been a model in which the telecommunications technologies,theories and ideas and those for the computer and the Internet are highly integrated,and the definition of pervasive services out of it is most typical.

Besides these direct definitions,there are still a lot of technical researches and descriptions closely related to pervasive services.For example,the Virtual Home Environment(VHE),proposed by 3GPP,and OMA Service Environment(OSE),defined by Open Mobile Alliance(OMA),have different visions of seamless ubiquitous services in the future,which are very similar to the concept of pervasive services.

From various descriptions of pervasive services,it can be concluded that pervasive services symbolize the demands and expectations from future services from the telecommunications,computer and Internet fields.Pervasive services have the following features:

·Pervasiveness:A user is able to enjoy services anywhere,anytime and by any access methods.

·Mobility:A user on the move can have a continuous service experience without any interruption.

·Transparency:The network complexity is transparent to both users and Service Providers(SP).

·QoS-Guarantee:QoSis controllable and ensured.

·Customization:Users can customize personalized services;SPs can discover users'preferences by data mining;the services represent users'preferences and characteristics.

·Adaptiveness:Services can make adaptive adjustment according to users'context,so as to offer users with better experience.

·Security:Service provisioning is secure,and users'privacy should be protected.

·Easiness:It is easier for users to use services;human-machine interaction is more convenient and flexible.

·Variety:Services have more types and more powerful functions.

·Time-to-Market:Services have a shorter development period,and are easier to be developed.

2 Development of Pervasive Services and Relevant Technologies

This part will introduce typical technologies,standards and research projects for pervasive services.The technologies and standards discussed here are those that have been mature and widely recognized by the industry while the research projects include pioneering and exploratory technologies.

2.1 Technologies and Standards for Pervasive Services

The main standardization organizations working on pervasive services include 3GPP,OMA,ETSI,Parlay Group and W3C.Their representative technologies and standards are as follows:

(1)VHE

The VHE［6］,defined by 3GPP,is an important feature of 3G/UMTSservices.It enables users to roam around different networks using their personal service environments at all time,just like they are in their home networks.The VHEfunction is fulfilled by the network intelligence-based technologies.It has requirements on service mobility and transparency;therefore,it can be regarded as a requirement subset of pervasive services.3GPPproposes severaltechnologies to implement the VHE,including Customized Application for Mobile Network Enhanced Logic(CAMEL),Open Service Access(OSA),Mobile Station Application Execution(MExE),UMTSSIM Application Toolkit(USAT).Moreover,such technologies as Mobile Agent(MA)can also be used for implementing the VHE［7］.

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(2)OSA

OSA［8］is an open service architecture jointly proposed by 3GPP,ETSIand Parlay Group.It abstracts the capabilities of a communications network as a set of Application Programming Interfaces(APIs)that are open,standard and independent of specific technologies for application implementation.The APIs are used for the development of services and applications by SPs,third-party service developers,independent software providers and other developers.The OSA can hide network complexity,facilitating the quick development and large-scale deployment of new services.Therefore,the OSA is a solution to transparency,variety and time-to-market of pervasive services.

The OSA provides two APIs:OSA/Parlay APIand Parlay XWeb Service.

The OSA/Parlay APIis defined based on Parlay APIof Parlay Group,and was first released in 3GPPR5 jointly by 3GPP,ETSIand Parlay Group.It has obtained the support of several international technology organizations like 3GPP2,JAIN and OMG.The latest version of OSA/Parlay APIis OSA v7.0.0/Parlay 6.

Although the OSA APIaims to enable numerous third-party SPs with no telecommunications network knowledge to develop telecommunications services,it has been found in practice that the OSA APIis still so complicated that developers are required to know much about telecommunications networks.Therefore,Parlay Group redefined the OSA/Parlay APIas an interface for service development in telecommunications networks［9］at its meeting held in May 2005.

3GPPR6 defines Parlay XWeb Service to facilitate third-party SPs to develop telecommunications services.The Parlay XWeb Service was originally defined by Parlay Group.Compared to the OSA API,Parlay Xis designed thoroughly for SPs without telecommunications network knowledge.It abstracts network capabilities at the higher layers,and completely shields the details for the implementation of network technologies.Therefore,it is simpler to use.However,Parlay Xcan only provide basic network capabilities.Its capabilities are much weaker than those of OSAAPI.The latest version of Parlay X is OSA Parlay Xv7.2.0/Parlay X 3.0.

(3)OSE

OMA［10］focuses on the research of service enablers.It has released more than 10 specifications on service enablers,such as Push-to-Talk over Cellular(POC),Instant Messaging(IM)and Device Management(DM),having significant influence in the value-added services field.However,since OMA was founded as a composition of several individualstandardization organizations,each of which focuses on a single service enabler,the work groups inside OMA lack coordination and often have overlapping or contradictory research subjects.For example,originally the POC work group and the IM work group defined the capabilities of presence and group list management respectively.In order to change this situation,OMA has made a series of adjustments,for instance,it has established an independent working group to study common capabilities like presence.Moreover,OMA defines the concept of OSE［11］,integrating a large number of OMA service enablers into the OSEfor unified management,and providing SPs with authorized service enabler access by the policy enforcer.Similar to OSA,OSEand its service enablers are technologies for the transparency,variety and time-to-market features of pervasive services.The OSEv1.0 has been released,but it is not mature,and is not accepted by the industry.OMA is conducting a deeper research and promotion of OSE,and is simultaneously looking for solutions to integrate OSEto the 3GPPOSA.

2.2 Pervasive Services Research Programs

There are a number of B3G research programs involving pervasive services,three of which are introduced in the following:

2.2.1 ISTof EU FP

The ISTof EU FP［12］studies B3G with broad subjects.It has attracted a large number of participants including universities,research institutes,standardization organizations,operators,equipment vendors and SPs,forming an alliance integrating research,production and application.The ISThas such pervasive service project clusters as Mobile Service Platforms and B3G System Architecture and Control,and several large-scale projects like DAIDALOS,SPICEand AMBIENT Networks are included［4］.In the FP6(2002-2006),DAIDALOSproposed the basic pervasive service environment structure including the entities like Service Provision Platform(SPP)and Pervasive Service Platform(PSP),defined and implemented new service components,and established a converged B3G trail network including the access and service networks.Moreover,DAIDALOSpaid great attention to the research of solution to the integration of its architecture with current network architectures of ITU and 3GPP［13］.

The IST's study on pervasive services concerns their pervasiveness,mobility,transparency,adaptiveness and security.

2.2.2 Research Programs in China

(1)“Fundamental Research on the Architecture of Universal Trustworthy Network and Pervasive Services”in the National Basic Research Program of China(973 Program)

This program［14］studies pervasive services in view of NGI.Its ideas are to propose an analytic theory of service and connection identifications based on an all-IPtrusted and converged network,to establish its mapping model and mechanism,and to enable the implementation of various services through a unified service interface.The program focuses on the QoS-guarantee,mobility and security features of pervasive services.

(2)“Service Network Intelligence”sponsored by the National Science Fund for Distinguished Yong Scholars

This program studies pervasive services from the view of B3G/NGN.In order to solve the problem that the tight coupling of the legacy bearing network and services prevents the provision of pervasive services in heterogeneous networks from providing pervasive services,it aims to propose a new environment for service development,deployment,operation and management in the viewpoint of service developers and SPs,with a goal of realizing transparent network access,abstracted network capabilities,layered network structure,open interface protocols,simple service development,pervasive services provisioning,distributed service resources,integrated service management,smooth service evolution and automatic service interaction.The program focuses on the transparency,customization,adaptiveness,push,variety and time-to-market features of pervasive services.

3 Development Trends and Hot Research Topics of Pervasive Services

3.1 Development Trends

Pervasive services and their relevant technologies tend to cooperate and converge.

(1)The understandings and research goals of pervasive services,with or without a research background of pervasive computing,B3G/telecommunications or computer/Internet,tend to unite.For example,at the ICPSinternational meetings,researchers with different research backgrounds can issue papers and discuss on the same subject,which shows a fact that the understandings of pervasive services are close enough.

(2)The technologies for pervasive services tend to converge.For example,the research of B3G learns much from pervasive computing technologies;OMA is proactively finding a solution to the convergence of OSEand OSA.

Pervasive services have the same development trends as network convergence,and they are expected to arrive at the same end.

3.2 Latest Research of Pervasive Services

The research plan of ISTin FP7(2007-2013)is taken here as an example to discuss the latest research on pervasive services［4］.

The ISTin FP7 has set up the Information and Communications Technology(ICT)Working Plan with a title of“Pervasive and Trusted Network and Service Infrastructures”.Compared to FP6,its FP7 has the following important features:

(1)The demand on the pervasive service environment willbe changed from“human”connection to“things”connection,which means the number of“users”will rocket.Therefore,a solution to network scalability is necessary.

(2)The security and trust mechanism is required to develop from the current add-on model to a built-in model.This does not mean that the network with a built-in security and trust mechanism will be completely safe,but it will facilitate the expansion of the security solution when necessary.

The achievements of FP7 are expected to promote technological standardization,enforce the leading position of ISTin the industry,and push forward the development of relevant industries(especially in the Internet field).

3.3 Hot Technologies for Pervasive Services

·Context Awareness:discovering potentialdemands of users by achieving and analyzing their context(including location,status and environment),using potential information to fulfill intelligent and human-based services

·Service Enabling:abstracting capabilities in the pervasive services environment to form various service enabler,providing simple and easy service development interface

·Service Management and Access Control:guaranteeing the normal and orderly use of service enabling components by their management and access control

·Pervasive Service Software System:developing generic,flexible,scalable and high-performance pervasive service software system by software engineering

·Service Discovery,Composition and Creation:Using technologies such as semantic network to implement automatic discovery,combination and creation of services.

4 Conclusion

The development of pervasive services and relevant technologies is in progress.Various viewpoints,ideas and technologies are maturing out of numerous collisions and communications,and they tend to converge with each other.