Anelise Munaretto

QoS for Ad hoc Networking Based on Multiple Metrics: Bandwidth and Delay

A link state routing approach makes available detailed information about the connectivity and the condition found in the network. OLSR protocol is an optimization over the classical link state protocol, tailored for mobile ad hoc networks. In this article, we design a QoS routing scheme over OLSR protocol, called QOLSR. In our proposal, we introduce more appropriate metrics than the hop distance used in OLSR. In order to improve quality requirements in routing information, delay and bandwidth measurements are applied. The implications of routing metrics on path computation are examined and the relational behind the selection of bandwidth and delay metrics are discussed. We first consider algorithms for single-metric approach, and then present a distributed algorithm for multiple metrics approach. We also present a scalable simulation model close to real operations in Ad Hoc Networks. The performance of our protocol are extensively investigated by simulation. Our results indicate that the attained gain by our proposal represent an important improvement in such mobile wireless networks.

Optimal path selection in a link state QoS routing protocol

A link state routing approach makes available detailed information about the connectivity and the topology found in a network. The OLSR (optimized link state routing) protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. OLSR introduces an interesting concept, multipoint relays (MPRs), to mitigate the message overhead during the flooding process. The heuristic for MPR selection limits their number in the network and ensures that the overhead is as low as possible. However, there is no guarantee that OLSR finds the optimal path in terms of QoS requirements. Moreover, in QoS routing, if the same heuristic used in the standard OLSR protocol for MPR selection is applied, the good quality links may be hidden to other nodes in the network. We introduce two algorithms for MPR selection based on QoS measurements. Analysis, numerical evaluation and simulations are presented. We show that the QOLSR protocol with the second proposed algorithm for MPR selection (QOLSR/spl I.bar/MPR2) finds optimal widest paths on the known partial network topology and presents the best performance.

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.

A link-state QoS routing protocol for ad hoc networks

A quality-of-service (QoS) routing protocol is developed for mobile ad hoc networks. We perform the proposed QoS-based routing in the optimized link state routing (OLSR) protocol, introducing a more appropriate metric than the hop distance. In our simulations the QoS routing protocol produces better performance comparing with the best-effort OLSR protocol.

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.

Comparing the energy efficiency of single-hop, multi-hop and incremental decode-and-forward in multi-relay wireless sensor networks

In this paper we analyze the energy efficiency of single-hop, multi-hop and incremental decode-and-forward in wireless sensor networks composed of multiple nodes. The energy efficiency analysis is constrained by a target outage probability and an end-to-end throughput, while the Nakagami-m distribution is used to model the small scale fading. Our results show that in most scenarios the cooperative incremental decode-and-forward scheme is more energy efficient than the other methods.

CGrAnt: a swarm intelligence-based routing protocol for delay tolerant networks

This paper presents a new routing protocol for Delay Tolerant Networks (DTNs), based on a distributed swarm intelligence approach. The protocol is called Cultural Greedy Ant (CGrAnt), as it uses a Cultural Algorithm (CA) and a greedy version of the Ant Colony Optimization (ACO) metaheuristic. The term greedy implies the use of a deterministic transition rule to exploit previously found good paths or explore new paths by selecting, from among a set of candidates, the most promising message forwarders. CGrAnt chooses each next node toward the message destination based on pheromone concentration (i.e., global information) whenever it is available. However, as the pheromone is not always available due to connectivity partitions, local information (i.e., heuristic function) captured from DTN nodes also supports a routing decision. Specific metrics and information gathered from the evolution are stored in Situational, Domain, and Historical Knowledge. The knowledge composes the CAs belief space, which is used to guide and improve the search. CGrAnt is compared with two DTN routing protocols (Epidemic and PROPHET) in an activity-based scenario. The results show that CGrAnt achieves a higher delivery ratio and lower byte redundancy than Epidemic and PROPHET.

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.

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.

Virtual time synchronization for multimedia ad hoc networks

We propose a novel protocol to deal with the synchronization problem of multimedia ad hoc networks. Our proposal eliminates the need for hard clock synchronization by implementing a virtual scheme that relies on the desynchronization between nodes. Such a decision is made because of the dynamic nature of the network topology. Therefore, the proposed algorithm computes the clock offsets between a node and each one of its one hop neighbors. We formulate our algorithm by deriving simple expressions combining stochastic and measured parameters. The proposed algorithm is validated through implementation and the results show that high levels of synchronization are achieved.