Catálogo de publicaciones - libros

Trends in fourth generation (4G) wireless networks are clearly identified by the concept where all traffic (data, control, voice and video services, etc.) will be transported in IP packets. MObile NETwork (MONET) is a group of mobile nodes moving together as a unit. Such groups are common characteristics of the vehicular environments, for example train and buses (which are attractive because of the high concentration of passengers on these vehicles). This paper investigates an ad hoc networking for Inter-MONET communications and interworking between MONETs and the global Internet. We propose a hierarchical architecture: (1) integrating Mobile IPv6 and OLSR, a routing protocol for ad hoc networks, to manage universal mobility; (2) connecting this ad hoc network to Internet. The heterogeneous communication is established with the help of specific access routers, which serve as gateways. We describe the network scenario, its basic protocol architecture and we discuss the different practical approaches for routing. A flat and hierarchical ad hoc routing comparison is studied and performance differentials are analyzed through simulation results using varying network load and mobility.

OLSR is a promising routing protocol for multi-hop wireless networks, recently standardized by the IETF. It intensively uses the concept of MPR to minimize the routing messages and limit the harmful effects of the broadcasting in such networks. In this article, we are interested in the performances of the Multi-Point Relay selection. We analyze the mean number of selected MPR per node and their spatial distribution with a theoretical approach and simulations. Then, we discuss the implications of these results on the efficiency of a broadcasting and on the reliability of OLSR when links between nodes may fail.

Cooperative relaying enables nodes to actively cooperate to deliver packets to their destination. The bestselect protocol (BSP) implements a type of cooperative relaying that generalizes single path routing with sets of nodes (relay-sets) replacing the concept of a single node relay. Thus, while in traditional single path routing, packets hop from node to node, in BSP, packets hop from relay-set to relay-set. Through the exchange of channel gain information between relay-sets, the best node within a relay-set is selected to transmit the data packet on behalf of the entire relay-set. The node selected depends on the metric used. Any metric that can be posed in a dynamic programming framework can be used. In this paper, performance gains from a number of selection metrics are investigated. Specific selection metrics include maximizing the minimum channel gain along the path, minimizing end-to-end delay, minimizing the total power, and minimizing the total energy. It will be shown that BSP can achieve significant gains in all of these metrics.

Providing differentiated Quality of Service (QoS) levels is an important challenge for wireless ad hoc networks and wireless LANs when applications have diverse performance requirements. The IEEE 802.11e MAC protocol can provide a Dynamic MAC by assigning different AIFSs, contention window expansion factors (PFs), and (, ) pairs for different classes and can provide a Static MAC by adjusting the durations of AIFSs based on priority levels [Aad01]. In this paper, we propose a novel and efficient service differentiation mechanism via the C-MAC. In our protocol, each node will change its backoff counter based on both its own packet’s priority level and the priority level of the transmitted packet. The simulation results indicate that the Static MAC provides a service differentiation at the expense of significant goodput degradation when the amount of high priority class traffic is low. On the other hand, the Dynamic MAC fails to prevent low priority classes accessing the channel resulting in significant high priority class goodput degradation when the network load is high. However, our mechanism always provides an efficient service differentiation mechanism and high goodput with a small goodput degradation.