From ULLA Towards UDAE

The design of Universal Data Access Engine (UDAE) was initially inspired by the Unified Link-Layer API (ULLA) design. Originally, ULLA was designed to abstract away the differences in link-layer technologies. It provides a unified way to retrieve link-layer information in a flexible and usable manner. It was evaluated in several kinds of resource limited devices such as Linux/notebook, Windows CE/PDA and TinyOS/TelosB motes. In addition to ULLA, we have further extended the concept of link-layer abstraction to general data abstraction. This concept enables a wider range of applications that can significantly benefit from UDAE. In the original ULLA approach, only lower layer and technology-specific components such as link-layer and sensing ones are employed. In UDAE, we present a more generic architecture which also copes with the application data provided by Data User components.

Universal Data Access Engine (UDAE)

What is UDAE? UDAE is a Universal Data Access Engine for wireless sensor networks. The UDAE allows developers to access data both locally and over the network from a variety of sources, such as sensors, communications links and platform components in a unified manner. It is also fully extensible, allowing data sources and users to be added flexibly at run-time. We have implemented UDAE for two operating systems (Contiki and TinyOS). While the TinyOS implementation has been done as native code, the Contiki implementation is based on a reconfigurable componentoriented middleware enabling developers to fully benefit from the flexibility offered by the UDAE.

Why Data Abstraction?

Writing distributed applications for WSNs has traditionally been a complicated affair. Until recently, it was customary to obtain sensor readings by accessing platform-specific registers and to develop the functions needed to process and exchange the obtained data in application specific manner. Such an approach obviously wastes resources and distracts the developer from focusing on the core functionality of his/her application. To remedy the situation, various ways to abstract data present in the sensor networks for easier manipulation and access have been developed. In this section we briefly discuss the data and communication abstraction problem for WSNs in general, and then compare the abstraction offered by the UDAE with other solutions presented in the literature.

UDAE Architecture

The main component called UDAE Core is an intermediate component connecting Data Providers(DPs) and Data Users(DUs). DUs are applications that read out data through UDAE Core via Data User interface. DPs are used to hide the difficulities to retrieve the specific information which ranges from lower layer to application layer information. At the abstract level, UDAE enforces that all components provide the common UDAE interfaces (Data Provider and Data User interfaces) and receptacles in order to specify their dependencies that are chained to compose applications. This introduces a clear separation between components which are entirely independent to each other. Consequently, the simplification of the developing process would be two-fold. First, DU developers control and retrieve information from the other components at a high level of abstraction. Second, DP developers are more interested in providing a UDAE-equipped software component over their technology or protocol.

Enabling Cross-Component Optimization with UDAE

A potentially significant application of UDAE that is inherently architectural in nature is cross-component optimization. By this we understand the obvious generalization of cross-layer optimization problem into the component-oriented setting. It has been argued by several authors that having dedicated cross-component interfaces for sharing information for optimization purposes does not scale. This is not only because of the quadratic scaling of the number of needed wirings as the function of the instantiated component counts, but also because of the need for customizing the interaction for each pair of components. This problem can be partially solved by having a common inter-component signaling mechanism, for which purpose the UDAE is very well suited.

Link to the UDAE Project at SourceForge

http://sourceforge.net/projects/udae/

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Contact

Krisakorn Rerkrai

Department of Wireless Networks
Kackertstraße 9
D-52072 Aachen
Tel: +49 / 2407 / 575-7054
Fax: +49 / 2407 / 575-7050