Abstract. With the development of sensor technology and electronic miniaturization, wireless sensor networks have shown a wide range of promising applications as well as challenges. Early stage sensor network analysis is critical, which allows us to reveal design errors before sensor deployment. Due to their distinguishable features, system specification and verification of sensor networks are highly non-trivial tasks. On the other hand, numerous formal theories and analysis tools have been developed in formal methods community, which may offer a systematic method for formal analysis of sensor networks. This paper presents our attempt on applying formal methods to sensor network specification/verification. An integrated notation named Active Sensor Processes is proposed for high-level specification. Next, we experiment formal verification techniques to reveal design flaws in sensor network applications. 1

Many wireless sensor network applications rely on the availability of a collection service to route data packets towards a sink node. The service is typically accessed through welldefined interfaces so as to hide the details of its implementation. Providing for efficient network operation, however, often requires investigating the interplay between specific collection services and application-level algorithms. To enable a smooth evaluation of these mutual dependencies, we implemented a reference collection protocol, known as CTP, as a module for the Castalia wireless sensor networks simulator. Castalia is a wellknown and widely used simulator but its standard distribution only provides for a basic collection module. By implementing a more advanced protocol like CTP we extend and improve the application scope of Castalia. In this report, we describe our implementation and present a study of the performance of CTP. All the software modules developed in the context of this work are available upon request from the authors. 1

Wireless sensor networks consist of resourceconstrained nodes; especially with respect to power resources. In many cases, the replacement of a dead node is difficult and costly, e.g. an implanted node in the human body. Our main goal in this paper is reducing the total power consumption of the network. For this purpose, we consider the cooperation of nodes in data transmission in terms of a group, since the major consumer of power is the data transmission process. A mobile node may move to a new location, in which it is desirable for the node to join a group. In this paper, we propose an algorithm for nodes to choose the best group in their signal range, using coalitional game theory to determine what is beneficial in terms of power consumption. The protocol is formalized in rewriting logic, implemented in the Maude tool, and validated by means of Maude’s model exploration facilities. Simulation-based tools are in general not able to prove the protocol. However, by using Maude, we prove the correctness of our proposed protocol, by searching for failures of the protocol, through all possible behaviors of sensors. These searches prove that grouping nodes is done correctly in all reachable states from a set of initial states of the model. In addition, we simulate our model in order to quantitatively analyze the efficiency of the proposed protocol. The results show significant improvements in power efficiency. 1.

The Collection Tree Protocol (CTP) is a well-know protocol that provides a reliable collection service for wireless sensor networks. In this report, we describe our implementation of CTP for the version 3.0 of the Castalia wireless sensor networks simulator. Besides being a reference for researchers interested in experimenting with CTP in Castalia, this report also provides a throughout description of the mechanisms of CTP. As the structure of our Castalia-based implementation mimics that of CTP’s TinyOS 2.1 components, the report also offers several insights into the details of such components. A former implementation of CTP for Castalia 1.3, which we had described in previous work [8], is no longer supported. The module implementing CTP for Castalia 3.0 is publicly available at

Abstract. Wireless sensor networks are typically ad-hoc networks of resource-constrained nodes; in particular, the nodes are limited in power resources. It can be difficult and costly to replace sensor nodes, for instance when implanted in the human body. Data transmission is the major consumer of power, so it is important to have power-efficient protocols. In order to reduce the total power consumption in the network, we consider nodes which cooperate to transmit data. Nodes which cooperate, form a group. A mobile node may at some point be without a group, in which case it is desirable for the node to be able to join a group. In this paper we propose a modification of the AODV protocol to decide whether a node should join a given group, using coalitional game theory to determine what is beneficial in terms of power consumption. The protocol is formalized in rewriting logic, implemented in the Maude tool, and validated by means of Maude’s model exploration facilities. 1

Wireless sensor networks consist of resource-constrained nodes; especially with respect to power resources. Often, the replacement of a dead node is difficult and costly; e.g. a node may be implanted in the human body. Therefore, it is important to reduce the total power consumption of WSNs. The major consumer of power is the data transmission process. This paper considers nodes which cooperate in data transmission in terms of a group. A mobile node may move to a new location, in which it is desirable for the node to join a group. We propose a protocol to allow nodes to choose the best group in their signal range, using coalitional game theory to determine what is beneficial in terms of power consumption. The protocol is formalized as an SOS-style transition system. This formalization forms the basis for an implementation in the rewriting logic tool Maude, so the protocol can be validated using Maude’s model exploration facilities. First, we prove the correctness of our proposed protocol, by searching for failures through all possible behaviors for given initial states. For these searches, the grouping is done correctly in all reachable final states of the model. Second, we simulate the model behavior to quantitatively analyze the efficiency of the proposed protocol. The results show significant improvements in power efficiency. This work was done in the context of the project Connect funded by the Norwegian Research Council and the EU project FP7-231620 HATS.

Abstract. Wireless sensor networks (WSNs) consist of resource-constrained nodes; especially with respect to power. In most cases, the replacement of a dead node is difficult and costly. It is therefore crucial to minimize the total energy consumption of the network. Since the major consumer of power in WSNs is the data transmission process, we consider nodes which cooperate for data transmission in terms of groups. A group has a leader which collects data from the members and communicates with the outside of the group. We propose and formalize a model for data collection in which mobile entities, called data MULEs, are used to move between group leaders and collect data messages using short-range and low-power data transmission. We combine declarative and operational modeling. The declarative model abstractly captures behavior without committing to specific transitions by means of probability distributions, whereas the operational model is given as a concrete transition system in rewriting logic. The probabilistic, declarative model is not used to select transition rules, but to stochastically capture the result of applying rules. Technically, we use probabilistic rewriting logic and embed our models into PMaude, which gives us a simulation engine for the combined models. We perform statistical quantitative analysis based on repeated discrete-event simulations in Maude. 1