Fusion Techniques for Reliable Information: A Survey <s> Robust, Consensus and Fault Tolerant Fusion <s> We introduce the concept of fusible data structures to maintain fault-tolerant data in distributed programs. Given a fusible data structure, it is possible to combine a set of such structures into a single fused structure, that is smaller than the combined size of the original structures. When any of the original data structures is updated, the fused structure can be updated incrementally using local information about the update and does not need to be entirely recomputed. In case of a failure, the fused structure, along with the correct original data structures, can be used to efficiently reconstruct the failed structure. We show that many commonly used data structures like arrays, hash tables, stacks and queues are fusible and we present algorithms to fuse and recover such structures. This approach often requires significantly less space than conventional backups by replication and still allows efficient operations on the original data structures. For example, our experiments on a distributed system suggests that for a system with k servers, this approach requires k times less space than replication based techniques. <s> BIB001 </s> Fusion Techniques for Reliable Information: A Survey <s> Robust, Consensus and Fault Tolerant Fusion <s> Beihang Univ, Sch Automat Sci & Elect Engn, Beijing 100083, Peoples R China. Chinese Acad Sci, Inst Software, Human Comp Interact & Intelligent Informat Proc L, Beijing 100080, Peoples R China. <s> BIB002 </s> Fusion Techniques for Reliable Information: A Survey <s> Robust, Consensus and Fault Tolerant Fusion <s> Sensor failures in process control programs can be tolerated through application of well known modular redundancy schemes. The reliability of a specific modular redundancy scheme depends on the predefined number of sensors that may fail, f, out of the total number of sensors available, n. Some recent sensor fusion algorithms offer the benefit of tolerating a more significant number of sensor failures than modular redundancy techniques at the expense of degrading the precision of sensor readings. In this paper, we present a novel sensor fusion algorithm based on randomized voting, having linear - O(n) expected execution time. The precision (the length) of the resulting interval is dependent on the number of faulty sensors - parameter f. A novel reliability model applicable to general sensor fusion schemes is proposed. Our modeling technique assumes the coexistence of two major types of sensor failures, permanent and transient. The model offers system designers the ability to analyze and define application specific balances between the expected system reliability and the desired interval estimate precision. Under the assumptions of failure independence and exponentially distributed failure occurrences, we use Markov models to compute system reliability. The model is then validated empirically and examples of reliability prediction are provided for networks with fairly large number of sensors (n>100). <s> BIB003 </s> Fusion Techniques for Reliable Information: A Survey <s> Robust, Consensus and Fault Tolerant Fusion <s> This paper presents a practical application called "activity map" to serve as guidance to show ambient intelligence-related contextual information gathered from both humans and their surrounding environments. The activity map utilizes results inferred from a location-aware activity recognition approach to statistically show a resident's possibly interleaved activities along with corresponding location-related contexts. With observations from a variety of multi-modal and non-intrusive wireless sensors, the approach utilizes a Bayesian network fusion engine with inputs from a set of the most informative features extracted from the sensors and applies joint inference to improve the accuracy and consistency of activity and location estimates. Additionally, each feature has to reckon its corresponding reliability factor to control its contribution in case of possible device failure, therefore making the system more tolerant to inevitable disturbance commonly encountered in a cluttered home environment. This mechanism can cope with some inherent sensor limitations and noise interference, thus improving overall robustness and performance. All experiments were conducted in an instrumented living lab and their results demonstrate the effectiveness of the system. <s> BIB004 </s> Fusion Techniques for Reliable Information: A Survey <s> Robust, Consensus and Fault Tolerant Fusion <s> Wireless sensor networks are resource-constrained self-organizing systems that are often deployed in inaccessible and inhospitable environments in order to collect data about some outside world phenomenon. For most sensor network applications, point-to-point reliability is not the main objective; instead, reliable event-of-interest delivery to the server needs to be guaranteed (possibly with a certain probability). The nature of communication in sensor networks is unpredictable and failure-prone, even more so than in regular wireless ad hoc networks. Therefore, it is essential to provide fault tolerant techniques for distributed sensor applications. Many recent studies in this area take drastically different approaches to addressing the fault tolerance issue in routing, transport and/or application layers. In this paper, we summarize and compare existing fault tolerant techniques to support sensor applications. We also discuss several interesting open research directions. <s> BIB005
Robust, consensus, or fault-tolerant is an important factor for research on fusion. Precise information about the sensed environment is scarce in the real world then the sensors are not always perfectly functional even if a multi-sensor fusion requires exact information about the sensed environment. A robust, consensus, or faulttolerant fusion technique should apply to the pervasive system. Some research progresses are performed. For instance, a robust fusion algorithm in the presence of the various forms of uncertainty is necessary in fusion systems BIB003 , BIB001 , BIB002 . The practical activity maps information in BIB004 shows ambient intelligence-related context information gathered from both humans and their surrounding environments. Principal strategies of the incorporating reliability into fusion operators are over-viewed in  . Fault-tolerant information fusion algorithms are proposed based on the generic statement of the Sensor Managements in BIB005 .