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 on Volume 53, Issue 2, May 2007 Page(s):

2 Outline Abstract Introduction Scenario Virtual Web Services Virtual Web Services Over DVB-H Conclusion

3 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.

4 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.

5 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.

6 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.

7 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.

8 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

9 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.

10 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.

11 Introduction - Purpose

12 Scenario

13 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.

14 Virtual Web Services – Architecture Who need Services Client software Web Services Service Provider Virtual Web Services

15 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.

16 Virtual Web Services – VWSDL & VWSEL Documents VWSEL }QOS }caching

17 Virtual Web Services – Development Cycle

18 Virtual Web Services – Production Cycle

19 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.

20 Virtual Web Services Over DVB-H – ESG Generation ←Broadcast time ←Accessing Information ←such as a WSDL

21 Virtual Web Services Over DVB-H

22 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.

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