Since the publication of the initial e-SENSE reference model, considerable effort has been spent in defining the initial e-SENSE system architecture. This deliverable document defines the initial e-SENSE system architecture which is work performed and led by Task 2.2 in WorkPackage 2 with the support of partners from Work Packages 2, 3 and 4. The involvement of other work packages in the specification process of the initial system architecture is crucial, as the system architecture aims to tie their future contributions and technical direction together into a coherent e-SENSE system.

The initial system architecture described in this report focuses mainly on the protocol stack architecture of the e-SENSE system. It details the service functions and service primitives offered by each of the subsystems in the e-SENSE protocol stack. The service functions cover all areas related to connectivity, management and middleware within the e-SENSE system. In addition to these service functions and their service primitives, service functions for security, privacy and trust addressing all e-SENSE subsystems are provided. The initial system architecture also includes an initial specification of service functions, required for gateways to beyond 3G mobile communication systems.

It rather creates the foundation of an architectural framework for all work packages and is expected to evolve to reflect the progress that will be made by the other work packages during the project. It should be therefore seen as an intermediate step towards the final overall e-SENSE system architecture. The final system architecture will be developed considering the research efforts of different work packages and described in the final deliverable D.2.2.2.

Section 2 of this document presents the logical architecture of the e-SENSE protocol stack and identifies interfaces between the different subsystems. As compared to initial version presented in the e-SENSE reference model, the protocol stack has further evolved. This section shows the updated logical architecture.

Section 3 of this document presents an initial specification of the connectivity subsystem.

Functional requirements for the connectivity subsystem are derived. Then appropriate service functions are specified and can be summarised in two categories, namely data transfer services and configuration services. The data transfer service of the connectivity subsystem facilitates the exchange of data within the e-SENSE system between sensor nodes as well as between sensor nodes and B3G communication systems. The functionality of the data transfer service is achieved by a co-operation of various protocol elements and mechanisms ranging from the PHY to network layer. The configuration service provides the means to configure the composition of the protocol stack, protocol parameters as well as internal state of the connectivity subsystem according to given requirements and application environment. Each service function of the data transfer service and configuration service is described in more detail. Furthermore respective service primitives provided at the service access points to other subsystems are specified.

Section 4 presents the middleware subsystem specification. Functional requirements for the middleware subsystem are identified. Appropriate service functions and their respective service primitives are developed and described in more detail. The service functions offered by the middleware subsystem can be grouped into context access service and node centric data service. The context access service offers a set of service functions that enables context aware applications to retrieve contextual information gathered by the e-SENSE system. Node centric data transfer service offer mechanisms for direct communication between nodes in the e-SENSE system. The middleware subsystem also comprises additional transport layer functionality on top of the data transfer services provided by the connectivity subsystem.

The management subsystem specification is described in Section 5. The management subsystem is responsible for the configuration and initialisation of the connectivity and middleware subsystems and provides supportive functionality to the e-SENSE system. The section describes functional requirements for the management subsystem and describes service functions and their service primitives. The identified service functions can be summarised in three categories according to their role: support services, management services and a programming service. The support services comprise service functions to support the operation of sensor nodes in the e-SENSE system. It includes functions required for service registration and discovery, device discovery, localisation and time synchronisation. The management services include all relevant service functions to manage the configuration and behaviour of a local sensor and, system wide, for the whole sensor network and ensure provision of appropriate security mechanism in the whole e-SENSE system. The programming service functions allow the life-cycle management of software components and data files on the sensor node.

Security is another important architectural aspect considered in this section. e-SENSE security, trust and privacy framework is developed in task T2.3 and aims to provide secure services that are light-weight and adaptive and reliably available despite exposure to various environmental conditions and security threats. Although the specification of the final framework is expected in deliverable D2.3.1 (M24), the initial system architecture detailed in this report is designed with security in mind. A first contribution is the inclusion of the security manager into the management subsystem of the e-SENSE protocol stack as presented in this report. Further attention has been given to the inclusion of security functions that are required to support the service functions in the subsystems throughout the e-SENSE protocol stack.

Section 6 presents a gateway architecture and relevant service functions that allow the integration of the e-SENSE architecture into “Beyond 3G” mobile and wireless communication systems. The design of the gateway architecture is an extension of the e-SENSE architecture and includes the interface between WSNs and “Beyond 3G” wireless systems. The gateway design is independent from the “Beyond 3G” solution and is studied as an extension of the current node design. Additional functionalities within the connectivity and middleware subsystems are reported to ensure access to B3G networks.

Section 7 briefly touches on aspects of adaptability and reconfiguration of the e-SENSE system. While the capability to adapt and reconfigure subsystems and protocol elements is considered in the design of the e-SENSE architecture, limitations of the sensor node capabilities and protocol stack architecture apply. This section therefore briefly explores how far this architectural feature is to be realised in the individual subsystems.

Section 8 briefly presents considerations for the design of a sensor node architecture, which is envisioned for the year 2 of the e-SENSE project. While surveying the current state of the art sensor node hardware and software platforms, expected challenges and initial direction for the development of sensor node architecture for the e-SENSE system are identified.