providing web services over dvb-h mobile virtual web services reporter: 藍元宏 date: 2009/05/11...
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Providing Web Services over DVB-H Mobile Virtual Web Services
Reporter: 藍元宏Date: 2009/05/11
Vilas, A.F.; Redondo, R.P.D.; Arias, J.J.P.; Solla, A.G.; Duque, J.G.Consumer Electronics, IEEE Transactions onVolume 53, Issue 2, May 2007 Page(s):644 - 652
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Outline
• Abstract• Introduction• Scenario• Virtual Web Services• Virtual Web Services Over DVB-H• Conclusion
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Abstract
• This paper introduces the experiences in accessing Web Services (WSs) from DVB-H terminals.
• This propose to move the complexity from client to the service provider by defining Virtual WSs (VWSs).
• Virtualization also gives the possibility of defining QoS-aware services as well as caching-based systems to process the responses of clients more efficiently.
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Introduction – Web Services
• Web Services (WSs) combine the best aspects of component-based development and the Internet.
• Web Services are accessed via ubiquitous Web protocols (ex: HTTP) and data formats (ex: XML).
• WSDL, UDDI and SOAP are considered the core of this Web Service standards set.
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Introduction – Web Services Limitation
• There are two relevant problems make it difficult to achieve this desirable open framework where flexibility is the key factor to communicate WSs and mobile clients.
• On the one hand, and inherently to the WS technology, clients are bound to a concrete service provider at design time.
• On the other hand, today’s mobile devices do not support the excessive complexity Mobile Web Services would need to allow changing the provider at run-time.
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Introduction – Solution
• This paper propose to introduce an intermediate virtualization layer between mobile clients and WS providers by using WS virtualization.
• A Virtual WS (VWS) is defined within this intermediate layer as a conceptual service grouping one or more WSs.
• A light client for this heavy virtual WS is delivered to the mobile receivers while the VWS is published as a standard WS.
• Client solves the complexity problems.
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Introduction – DVB-H Overview
• Regarding to delivering aspects, broadcasting is a highly cost-effective way to reach large audiences.
• DVB-H (Digital Video Broadcasting-Handheld) is considered a good candidate for being widely adopted, especially in Europe.
• DVB-H is forecast to be accessible by approximately 350 million mobile users by 2008.
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Introduction – The Advantages of DVB-H
• DVB-H is an approved standard by ETSI (European Telecommunications Institute).
• DVB-H benefits from existing DVB-T (DVB Terrestrial) infrastructure components, reducing initial investments.
• DVB-H is clearly supported by the majority of mobile device manufacturers like Motorola, Nokia, Samsung, LG, BenQ and Sagem
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Introduction – DVB-H Technology
• DVB-H has improved the DVB-T standard to overcome the communication problems derived from the inherent characteristics of small and portable devices.
• Time-slicing has been introduced to reduce the average power consumption of the receiver and to enable smooth and seamless frequency handover.
• It is incorporated a module of forward error correction for multiprotocol encapsulated data (MPE-FEC, Multiprotocol Encapsulation Forward Error Correction), which enhances the reception in the special conditions of handheld terminals.
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Introduction – DVB-H and IP Protocol
• IPDC (Internet Protocol Datacasting) is what converts DVB-H in an end-to-end broadcast system for delivering any type of digital content and services using IP-based mechanisms.
• Download by FLUTE (File deLivery over Unidirectional Transport) and streaming by RTP (Real Time Protocol) respectively.
• DVB-H ESG (DVB-H Electronic Service Guide) describes the available IP Datacast services.
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Introduction - Purpose
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Scenario
砰!!!
Location: {GPS value}Services Provider: Virtual Traffic Web ServicesTraffic Flow: {Slow, Sluggish, Free Flow}Incident: {None, Minor, Moderate, Severe}
Private Traffic Center1Government Traffic Center
Virtual Traffic Web Services
Private Traffic Center2
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Virtual Web Services – Overview
• Virtualization is an elegant solution to solve several open problems in WS technologies, like asynchronous invocation, error control, high availability, quality of service, etc.
• The binding process in WS technologies, binding at design-time, is an important limitation.
• WS virtualization is based on grouping one or more web services inside a unique wrapper, which is then published as a standard web service which called VWS.
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Virtual Web Services – Architecture
Who need Services
Client software
Web Services
Service Provider
Virtual Web Services
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Virtual Web Services – Implementation
• The implementation of this VWS is virtually defined by the VWSDL document (VWS Definition Language).
• VWSDL is an XML-based language which has been defined as a stand-alone language, i.e. not as a WSDL extension.
• VWSDL definition is only useful to a VWS engine.
• On top of VWSDL, this paper have defined VWSEL (Virtual Web Services Extension Language), which allows the clients to use SOAP-Header elements to add control information which modifies the behavior of the engine.
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Virtual Web Services – VWSDL & VWSEL Documents
VWSEL}QOS
}caching
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Virtual Web Services – Development Cycle
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Virtual Web Services – Production Cycle
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Virtual Web Services Over DVB-H
• DVB-H standard specifies two ways for broadcasting content by using, respectively, the RTP and FLUTE protocols.
• RTP contents are mainly devoted to TV-like broadcasting.
• Other binary objects (textual, applications, multimedia, etc.) can be delivered in a data carousel over FLUTE.
• Both kinds of contents can be locally accessed by using the information in the ESG.
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Virtual Web Services Over DVB-H – ESG Generation
←Broadcast time
←Accessing Information
←such as a WSDL
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Virtual Web Services Over DVB-H
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Conclusion
• This define an intermediate layer between the WS provider and the WS mobile client where virtualization is encapsulated, hiding complexity, availability and location problems to mobile clients.
• As complexity resides in the virtual Web Services, we have light clients, more adequate for mobile devices.
• By combining virtualization of services (through VWS) and broadcast infrastructures (FLUTE carousel over DVB-H); This paper enable mobile devices to access Web Services through the new open Web.
Thanks for your attention!!