CAC-OLSR: Extending OLSR to Provide Admission Control in Wireless Mesh Networks

This work presents an admission control mechanism for multi-hop wireless mesh networks based on the IEEE 802.11 standard and the OLSR routing protocol. This mechanism, called CAC-OLSR, aims at ensuring that traffic flows with quality of service (QoS) requirements, especially voice and video, are only admitted in the mesh network if it has available resources in order to provide flow requirements. In addition, QoS requirements of previously admitted traffic flows cannot be violated. The proposal was evaluated with NS-2 and Evalvid simulations.     

Context-Aware Routing in Delay and Disruption Tolerant Networks

In this paper, we analyze the problem of context adaptation in delay and disruption tolerant networks (DTNs). Initially, we performed experiments with well-known routing protocols to evaluate how much distinct configurations impact their performance. The results show that the performance is highly configuration dependent and improper configuration can lead to a performance up to 506.6 % worse than the best configuration tested. This motivates us to propose CARTOON (context-aware routing protocol for opportunistic networks), a novel routing protocol for DTNs based on the concept of context-adaptation. We evaluate CARTOON through simulations and the results show that our propose outperformed other well-known protocols, exhibiting results that are, on average, at 95 % of the computed optimum delivery rate.     

XTemplate 3.0: spatio-temporal semantics and structure reuse for hypermedia compositions

The use of declarative languages in digital TV systems, as well as IPTV systems, facilitates the creation of interactive applications. However, when an application becomes more complex, with many user interactions, for example, the hypermedia document that describes that application becomes bigger, having many lines of XML code. Thus, specification reuse is crucial for an efficient application development process. This paper proposes the XTemplate 3.0 language, which allows the creation of NCL hypermedia composite templates. Templates define generic structures of nodes and links to be added to a document composition, providing spatio-temporal synchronization semantics to it. The use of hypermedia composite templates aims at facilitating the authoring work, allowing the reuse of hypermedia document common specifications. Using composite templates, hypermedia documents become simpler and easier to be created. The 3.0 version of XTemplate adds new facilities to the XTemplate language, such as the possibility of specifying presentation information, the attribution of values to variables and connector parameters during template processing time and the template ability to extend other templates. As an application of XTemplate, this work extends the NCL 3.0 declarative language with XTemplate, adding semantics to NCL contexts and providing document structure reuse. In addition, this paper also presents two authoring tools: the template processor and the wizard to create NCL documents using templates. The wizard tool allows the author to choose a template included in a template base and create an NCL document using that template. The template processor transforms an NCL document using templates into a standard NCL 3.0 document according to digital TV and IPTV standards.     

Improving SMIL with NCM Facilities

SMIL is an XML-based language for specifying documents with temporal and spatial synchronization relationships, recommended by the W3C. However, SMIL has some limitations as a hypermedia authoring language. In order to overcome these limitations, this work presents the integration of SMIL documents with HyperProp, a hypermedia system based on an object-oriented model called NCM (Nested Context Model). As benefits, the integration makes both NCM facilities and HyperProp authoring and formatting tools available for SMIL documents. Furthermore, this work presents how the SMIL language can be extended to incorporate NCM facilities through the inclusion of new XML elements and attributes found in NCL, the NCM declarative language. Among the facilities, we can highlight the possibility of reusing document components and their presentation characteristics, offering flexibility in temporal specifications, adapting a document presentation according to user navigation and specifying n-ary relationships expressing causality or constraint among components.     

SDN-based teleprotection and control power systems: A study of available controllers and their suitability

With the popularization of the smart grid paradigm, substation automation technology has gradually been upgraded with additional processing and communication capabilities within control and protection devices. Hence, the research community is pressured to find new, efficient, and reliable communication solutions for such a scenario. That task is complicated by the stringent temporal requirements defined by the International Electrotechnical Commission (IEC) 61850 standard for power system communication comprising teleprotection schemes. Further compounding the issue is the critical nature of the power grid, in which availability is definitely a strong requirement. Software-defined networking (SDN) may provide powerful tools to fulfill those requirements at acceptable costs. As such, this paper surveys and compares several available SDN controllers and their applicability to the teleprotection scenario. It further evaluates controllers in terms of capacity and resilience through experiments in an emulated environment.