Catálogo de publicaciones - libros

Cross layering has recently emerged as a new trend to cope with performance issues of mobile ad hoc networks. The concept behind this technique is to exploit local information produced by other protocols, so as to enable optimizations and deliver better network performance. However, the need for a new interaction paradigm inside the protocol stack has to face with the legacy aspects of classical architectures (e.g., the Internet), where layer separation allows for easy standardization and deployment. In this paper, we show that cross layering can be achieved maintaining a clean architectural modularity, making protocols exchange information through a vertical interface. Specifically, we present the design of a cross-layer module, and provide a proof of concepts of its “usability” at different layers of the protocol stack, considering two case studies from a design and implementation standpoint.

The paper presents an emulation architecture working in the user space useful to implement and test routing protocols for ad hoc networks. The emulator interfaces with the Simple Ad hoc siMulator (SAM) [], where many routing protocols are present. The novelty with respect to SAM is the possibility to test routing protocols with a real exchange of signaling and data packets between the nodes present in the network. With respect to a live test, the emulator works on hosts connected each other via wired links and the wireless channel is simulated.

The integration of wireless local area network and wireless mobile devices allows to implement a complete information system able to support everyday activities unobtrusively and seamlessly as the ubiquitous computing paradigm says. Wireless mobile ad hoc networking could be successfully used in the construction of flexible and adaptive information system with no fixed infrastructure and it allows to covers multi-hop scenarios such as m-learning approaches. This paper describes choices and issues encountered in the adoption of wireless technologies as regards standards and topologies in order to realize a wireless network infrastructure suitable for teaching and learning Astrophysics using mobile devices. This study is part of the “Learning form Starlight” project presented by the Italian National Institute for Astrophysics to the Hewlett Packard Philanthropy foundation aiming at introducing in schools a new way of teaching and learning not strictly related to the classroom location context. The realization of this system outlines that the Wi-Fi standard in network deployment has up to now to be preferred to other available wireless technologies for the easiest way of set up connection and use and the possibility to implement different network topologies suitable for m-learning applications.

Re-use of existing widely explored Medium Access Control (MAC) schemes, like the well-known Aloha scheme, is not applicable in ad hoc networks where the transmissions of the users can be normally sensed by only a fraction of the users present in the network. Therefore, are not possible anymore. Here, an for medium access control in ad hoc networks, inspired by the Aloha paradigm, is proposed and analyzed. Simulation results show that this policy is capable of achieving higher when compared to other policies that have been proposed for ad hoc networks. It is also shown that severely impacts the system throughput and therefore, an alternative approach is proposed that reduces the effects of mobility in the expense of the maximum achievable system throughput.

Many broadcasting protocols for ad hoc and sensor networks have been proposed. Multipoint relay (MPR) and dominating set (DS) schemes can effectively improve the efficiency while providing reliable broadcasting. The neighbor elimination scheme (NES) can improve any broadcasting protocol as an added feature. We evaluate the performance of MPR (source dependent), MPR-DS (source-independent MPR), and DS-based protocols. We add NES to these schemes separately and evaluate the performance of the resulted protocols. As a result, DS-NES appears to be the most robust, taking all measurements and parameters into account, because it remains competitive under all scenarios, and has significant advantages over MPR-DS-NES in dynamic scenarios, and over MPR-NES when the broadcast message is not very large, because MPR has overhead in packet lengths.

Most of the previous efforts regarding multicast routing in MANETs, have been devoted to the provision of low-control overhead protocols, being able to maximize the packet delivery ratio. In multicast routing, the non-optimality of the forwarding structure can also lead to transmission of additional data packets (compared to the minimum required). We call those additional data packets data-overhead. In this paper, we present a counter-based forwarding elimination scheme, being able to reduce that overhead depending upon the mobility of the nodes. Our results show that this approach is able to enhance the bandwidth consumption of mesh-based multicast ad hoc routing protocols while maintaining nearly the same packet delivery ratio.

This paper discusses the usage of Ad-Hoc technologies as “hotspot extension” mechanisms. We propose a hybrid network where 802.16 links are used for providing high-bandwidth access, and local distribution is performed by Ad-Hoc network nodes, thus covering arbitrary areas around the 802.16 stations, which might be connected to the Internet. We evaluate the performance of the system and its efficiency in providing QoS in multicast connections. We propose two extensions of the ODMRP and MAODV routing algorithms by augmenting them with a zone routing behavior, thus producing two new hybrid multicast routing algorithms: ZODMRP and ZMAODV. The simulation results show that ZODMRP provides the highest packet delivery ratio and lowest delay without introducing large overhead.

This paper describes an algorithm for clustering an ad hoc network, in which the devices have highly varying resources. Such a heterogeneous ad hoc network is formed when wireless and fixed consumer devices like laptops, personal data assistants, cellular phones and servers automatically interconnect. The aim of clustering is twofold: to reduce broadcast traffic, which is typical to ad hoc routing protocols, and to concentrate traffic to devices with more available resources and less mobility. Further, the clustering process identifies nodes that are suitable for service provision. The algorithm is lightweight as it operates with a single periodically sent message. We provide simulation results that show the performance of the algorithm.

The main ad hoc routing protocols that were proposed generally provide only flat networks. However the Internet has always been of a hierarchical nature, for scalability and manageability reasons. This paper therefore introduces a simple mechanism providing dynamic clustering with OLSR, one of the MANET routing solutions, chosen for its ease of integration in the Internet infrastructure. This clustering can have many different applications. This work describes how it can be used to provide hierarchical routing with OLSR. However, it is not limited to this use.

We present an asynchronous software and hardware architecture specifically suited for wireless sensor network nodes. To reduce power consumption and/or increase performances, some blocks go into hardware. The whole system is modelled using a unique asynchronous HDL before being partitioned. The software part that is executed on an asynchronous processor is then scheduled using a quasi-static scheduling and operates in an event-driven way with reactive hardware through an interface controller. We use an asynchronous analog to digital converter combined to a new approach in the non-uniform signal processing theory to obtain an entire event-driven platform. The use of asynchronous hardware allows to efficiently design a fine-grained dynamic power consumption control mechanism controlling V (digital voltage scaling) and V (bulk biasing) in order to manage the speed/power consumption trade-off and to go in a low-power idle mode state with very few static leakage. Finally, to increase the lifetime of the nodes, some scavenging techniques are added.