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Ubiquitous and pervasive computing envisions context-aware systems that gather real world information from many fixed and mobile microchips and sensors integrated in everyday objects. To provide valuable services, it is necessary to estimate the location of users or objects. Outdoor location tracking is achieved by Global Positioning System (GPS), but due to its poor indoor coverage, there is a need...
We consider the on-demand delivery of layered video over peer-to-peer (P2P) networks. A parallel server architecture enables the service of requests by more than one server, thus reducing load at individual servers and dispersing network load. In a P2P network, peer upload bandwidth is limited and heterogenous, so a P2P streaming session may involve multiple supplying peers of different uplink. Partitioning...
A flexible wireless sensor network platform for easier implementation of diverse applications has been developed and deployed at the Institute Superior Tecnico - Technical University of Lisbon (IST-TUL). This test-bed integrates multiple projects into a single common network, thus creating an expandable platform that facilitates the development of future applications. To achieve this flexibility,...
Two-tiered sensor networks have gained popularity in recent years, due to their ability to facilitate load-balanced data gathering, fault-tolerance as well as increased network connectivity and coverage. Using higher-powered relay nodes as cluster heads can lead to further improvements in network performance. It is important to determine an appropriate placement scheme for such relay nodes, in order...
Different network applications need different Quality of Service (QoS) requirements such as packet delay, packet loss, bandwidth and availability. It is important to develop a network architecture which is able to guaranty quality of service requirements for high priority traffic. In Wireless Multimedia Sensor Networks (WMSNs), a sensor node may have different kinds of sensor which gather different...
The method of finding point of bending on efficiency curve in a distributed systems has been presented. The performance of distributed environment was studied as a cost function of mean network throughput and memory buffers availability. The method can be used then to build up an autonomic bandwidth management. The bounding point on efficiency curve was found as well analytically as for testing facility...
There have been a number of efforts devoted to predicting or modeling TCP performance under the presence of various network defects with a statistic such as average TCP throughput. While the average TCP throughput is useful, it does not provide insight on the variability of results that may be seen across multiple end users. This paper reports on a simulation study to characterize the distribution...
In this paper we present two novel approaches for voice indexing and search. The first approach is a Uniterm based voice indexing and search scheme that can be used for the fast retrieval of voice tagged multimedia contents on mobile devices. Uniterms, a string of phonemes with high scores, are extracted, in the indexing stage, from the phoneme lattice. For retrieval, the Uniterms are scored against...
Wireless sensor networks (WSN) consist of some nodes that have limited processing power, memory and energy source. These constraints cause the algorithms that presented in this field focus on these constraints. Data aggregation is any process in which information is gathered and expressed in a summary form. Data aggregation has been put forward as an essential paradigm for wireless routing in sensor...
Backoff algorithms in traditional distributed contention-based MAC protocols concentrate on adjusting contention window size to resolve collision. However, collision may still occur as long as these windows intersect with each other. In order to solve this problem, we put forward a collision classification model to classify collisions into cross collision and intra collision and suggest to solve them...
Understanding the communication behavior and network resource usage of parallel applications is critical to achieving high performance and scalability on systems with tens of thousands of network endpoints. The need for better understanding is not only driven by the desire to identify potential performance optimization opportunities for current networks, but is also a necessity for designing next-generation...
The advances in wireless communication and positioning technology have made it possible to collect large volumes of personal location data. While such data are useful to many organizations, making them public accessible is generally prohibited, because location data may imply sensitive private information. This paper investigates the challenges of publishing location data while preserving the location...
In peer-to-peer file sharing systems, file replication and consistency maintenance are widely used techniques for high system performance. Despite significant interdependencies between them, these two issues are typically addressed separately. Most file replication methods rigidly specify replica nodes, leading to low replica utilization, unnecessary replicas and hence extra consistency maintenance...
Wireless sensor networks are characterized by centralized data gathering, multi-hop communication and many to one traffic pattern. These three characteristics can lead to severe packet collision, network congestion and packet loss, and even result in hot-spots of energy consumption thus causing premature death of sensor nodes and entire network. The proposed load balance data gathering algorithm classifies...
The H.264/SVC video codec extends the H.264/AVC standard with scalability features. In this paper we introduce a traffic prioritization algorithm suitable for the transmission of both H.264/SVC and H.264/AVC video over 802.11e ad hoc wireless networks. The proposed algorithm exploits the traffic prioritization capabilities offered by 802.11e to provide better protection to the most perceptually important...
This paper presents a new protocol for Internet voting based on implicit data security. This protocol allows recasting of votes, which permits a change of mind by voters either during the time window over which polling is open or during a shorter period over which recasting is permitted [20]. The security of votes depends on multiple servers such that each vote is divided into partitions and these...
Broadcast presents a special challenge for wireless sensor networks (WSNs). In some situation such as time synchronization or building routing path, broadcasting messages must be securely transmitted to all nodes, but this process is subject to attack by adversaries. For example, an adversary may try to waste the battery power of intermediate nodes by forcing a compromised node to repeatedly rebroadcast,...
The use of sensor networks is increasing day by day; which offer more research topics to be discuss and modified; one of these topics is the power consumption that has to be reduced as possible, where the resources are limited; another topic is the security level that should be offer by such kind of networks. Clustered networks have been proposed in many papers to reduce the power consumption in sensor...
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