## 4 Related Works and Contemporary VSN Projects
### Sensor Network Virtualization Projects
#### 4.1.1 FRESnel  
FRESnel [40] stands for Federated Secure Sensor Network Laboratory. FRESnel is focusing to build a large scale federated sensor network framework with different applications sharing the same resources. The importance of this project is to ensure reliable intra-application communication as well as a scalable and distributed management infrastructure. It also ensures orthogonality, privacy and application security. The evaluation of the proposal is primarily through a large scale federation of sensor networks over the Cambridge University campus. The sensor nodes monitor different aspects such as temperature, pollution, movement, _etc._ and the network will be running various applications belonging to different authorities in the city or the coverage area. The overall aim of the project is to provide a federated sensor network platform that could be used by multiple applications in a seamless and secure manner. To achieve the goal, the project has focus on the following technical points:  
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* It will develop a language for service level description and agreement for this kind of sensor network sharing. The language will be the basis of resource and application management and monitoring framework.
* It will develop methodology to enable dynamic resource allocation in a decentralized fashion. The techniques will be designed to take into account application needs and network resources. It will be adaptive to varying application demands, scalable in terms of network resources, and robust to resource failures.
* It will identify the mechanisms for dynamic partitioning of the sensor network into application-specific virtual sensor networks. These mechanisms should protect nodes belonging to different partitions against each other, especially during the transitive phase of dynamic repartitioning. Protection is in the form of privacy preservation and observation of resource allocation boundaries.
* It will develop distributed and scalable communication protocols that will allow the components of a single sensor application to communicate with one another in a reliable, secured and efficient way. The underlying collection of nodes, which belongs to the same virtual sensor network, will be able to configure itself dynamically to include new resources and heal from network failures.
* It will develop distributed algorithms for processing queries with very different quality-of-service requirements for accuracy and delay. In the presence of high query loads, these algorithms should gracefully degrade the quality of query answers giving priority to address the needs of critical applications. Privacy policies may also require that the specificity of certain query answers be limited.
* It will deploy a prototype for federated sensor network around the University of Cambridge campus, also partially integrating existing sensor networks. This will be a limited version of the envisioned CityNet application. It will span different colleges and will cover heterogeneous monitoring needs ranging from room usage and college security by using cameras), to air quality by using bike-mounted bio-sensors and traffic monitoring by using vehicle-generated GPS trajectories forwarded to fixed nodes installed in different colleges.