Mauro Fonseca

Routing and quality of service support for mobile ad hoc networks

OLSR is an optimization over classical link state protocols tailored for mobile ad hoc networks. In this paper, we propose the QOLSR protocol which includes quality parameters to the standard OLSR. Three variants of QOLSR are introduced, taking into account the delay measurement together with the hop count metric. Then, we analyze new heuristics for the multipoint relay selection, and evaluate our proposed approaches comparing them with the standard OLSR protocol. Simulation results show that an increased load-balancing and a reduced dropped packets rate are achieved due to the inclusion of the delay information.

Error control coding in wireless sensor networks

Wireless Sensor Networks (WSN) are usually a set of battery-supplied small devices. One of the main challenges in deploying WSN is to improve energy-efficiency and lifetime of the nodes while keeping communication reliability. Transmissions over the wireless channel may experience many impairments, like random noise and fading, increasing the bit error rate at reception, causing several retransmissions, and consuming extra energy from the node. In order to minimize the harmful effects of the radio channel, error control strategies using packet retransmission and error correcting codes are commonly utilized. In this work we investigate the trade-off between transmission and processing energy consumption in a sensor node employing convolutional codes. Through this study we can identify and select the appropriate complexity of the error control code to be used in each sensor node, in order to maximize the network lifetime.

ZAP: a distributed channel assignment algorithm for cognitive radio networks

We propose ZAP, an algorithm for the distributed channel assignment in cognitive radio (CR) networks. CRs are capable of identifying underutilized licensed bands of the spectrum, allowing their reuse by secondary users without interfering with primary users. In this context, efficient channel assignment is challenging as ideally it must be simple, incur acceptable communication overhead, provide timely response, and be adaptive to accommodate frequent changes in the network. Another challenge is the optimization of network capacity through interference minimization. In contrast to related work, ZAP addresses these challenges with a fully distributed approach based only on local (neighborhood) knowledge, while significantly reducing computational costs and the number of messages required for channel assignment. Simulations confirm the efficiency of ZAP in terms of (i) the performance tradeoff between different metrics and (ii) the fast achievement of a suitable assignment solution regardless of network size and density.

Substituting COPS-PR: an evaluation of NETCONF and SOAP for policy provisioning

The COPS-PR protocol has been defined by the IETF to provide policy provisioning in networks managed through the policy-based network management approach. Although some network players already ship their devices with proper COPS-PR support, there is a trend in the industry and in the IETF of discontinuing COPS-PR as a policy protocol. Meanwhile, two other protocols, namely NETCONF and SOAP, have been seriously considered in the network management field. This paper proposes and evaluates both NETCONF and SOAP as substitutes for COPS-PR, presenting how these protocols can be used for policy provisioning. The performance evaluation of NETCONF and SOAP against COPS-PR addresses two main aspects: network usage as a result of protocol overhead, and protocol delay as a result of protocol message processing. This study shows that both NETCONF and SOAP are interesting and feasible replacements for COPS-PR, but require appropriate modeling when deployed in networks

An XML model for SLA definition with key indicators

This work proposes a XML-based model for the specification of service level agreements (SLA). The model has XML elements to define a semantic to represent key performance indicators (KPI) and key quality indicators (KQI) and the relationship between them. Upper and lower thresholds are associated to the indicators in order to indicate warnings or errors conditions. The relationship between the indicators is expressed by reusable functions which are evoked by the XML-based model. An example of reusable function for calculating the KQI service availability based on KPI indicators is also presented in this paper.

Optimal DiffServ AC Design using Non-Linear Programming

Most DiffServ admission control (AC) algorithms rely on tuning parameters to help in the decision making. Tuning these parameters is a difficult task, especially when one considers the problem of assuring QoS guarantees to individual flows. This paper proposes a method for helping the design of DiffServ AC algorithms based on non-linear programming optimization. It enables to find the values for the AC parameters that permits to satisfy the QoS guarantees for individual VoIP flows, while minimizing a cost function that represents the performance goals of the service provider. This approach is used to compare the performance of some commonly used DiffServ AC techniques and also to design a novel AC algorithm based on queue estimates.

Analysis of policy management models and specification languages

In this work, we will focus on the work undertaken in the specification of policies, the different notations developed, and how policies are deployed within a managed system. We will motivate, analyze, and classify all major existing policy notations through several criteria and try to consider the consistent merging of their strengths into a more appropriate framework. We also propose a set of enhancing features to existing policy specification notions namely domain membership rules, role compatibility rules, and light events. The work ends by an enumeration of the set of features which a policy specification language needs to model in order to facilitate the process of implementing adaptive Quality of Service management and rapid deployment of customized services.

Fair Time Sharing Protocol: A Solution for IEEE 802.11b Hot Spots

To adapt the data rate in accordance with the quality of the link, the IEEE 802.11b standard proposes the variable rate shifting functionality. This intrinsic functionality of the 802.11b products progressively degrades the bit rate when a host detects unsuccessful frame transmissions. Furthermore, the basic CSMA/CA channel access method guarantees that the long-term channel access probability is equal for all hosts. When one host captures the channel for a long time because its bit rate is low, it penalizes other hosts that use the higher rate, inciting a performance anomaly. This paper aims at avoiding this performance anomaly and the consequent waste of bandwidth.We propose the Fair Time Sharing (FTS) approach to perform real fair sharing among the active hosts in the hot spot, thus avoiding the performance degradation caused by one or more slow hosts. This paper presents the FTS architecture and its performance evaluation, showing the improvement achieved.

Multi-domain Policy Based Management Using Mobile Agents

This paper describes a new framework for the interoperability between ISP management domain for the purpose of satisfying end user requirement based on service level agreements (SLA) set up between a customer and its related ISP and also SLA set up between ISPs. The paper considers future policy based enabled equipments and management centers based on the ongoing work undertaken in the frame of the resource allocation protocol and policy framework groups of the IETF. The objective of this paper is to investigate the possibility to merge policy based management with mobile agents in order to handel QoS of communications spanning over a number of ISP domains. In this environment, mobile agents will act on behalf of users or third party service providers, to obtain the best end to end service based on a negotiation process between ISP policy management systems.

A social-aware routing protocol for opportunistic networks

Swarm intelligence-based approach designed to intermittently connected networks.Greedy Ant Colony Optimization and Cultural Algorithms to address the routing problem.The utility of nodes as message forwarders considers a set of socialaware metrics.Operational metrics characterize the opportunistic social connectivity between nodes.CGrAnt outperforms Epidemic, PROPHET, and dLife in message delivery and redundancy. Understanding nodes mobility is of fundamental importance for data delivery in opportunistic and intermittently connected networks referred to as Delay Tolerant Networks (DTNs). The analysis of such mobility patterns and the understanding of how mobile nodes interact play a critical role when designing new routing protocols for DTNs. The Cultural Greedy Ant (CGrAnt) protocol is a hybrid Swarm Intelligence-based approach designed to address the routing problem in such dynamic and complex environment. CGrAnt is based on: (1) Cultural Algorithms (CA) and Ant Colony Optimization (ACO) and (2) operational metrics that characterize the opportunistic social connectivity between wireless users. The most promising message forwarders are selected via a greedy transition rule based mainly on local information captured from the DTN environment. Whenever global information is available, it can also be used to support decisions. We compare the performance of CGrAnt with Epidemic, PROPHET, and dLife protocols in two different mobility scenarios under varying networking parameters. Results obtained by the ONE simulator show that CGrAnt achieves a higher message delivery and lower message redundancy than the three protocols in both scenarios. The only exception is in one of the scenarios, when messages have a time to live lower than 900 min, where CGrAnt delivers a bit less messages than dLife, although with a lower message redundancy.