28 research outputs found
Irresponsible forwarding
No full textIn a self-organizing traffic information system, vehicles share and distribute the traffic information by rebroadcasting a received information packet to their neighbors. However, it is inefficient to let every vehicle rebroadcast the information packet, since the redundant packets waste the valuable (finite) radio channel bandwidth. Reducing the number of redundant packets, while still ensuring good coverage and reachability, is one of the main objectives in multi-hop broadcasting. In this paper, we propose a new probabilistic-based rebroadcast scheme, denoted as Irresponsible Forwarding, where each vehicle rebroadcasts a received information on the basis of (i) its distance from the source and (ii) the density of its neighbors. The key idea is that a node implicitly evaluates the probability that there is another node which can rebroadcast more successfully: if this probability is sufficiently high, then the node ¿irresponsibly¿ does not rebroadcast. Unlike the other existing probability assignment schemes, our scheme also takes the statistical distribution of the vehicles on the road into consideration. Moreover, it will be shown that, for sufficiently large values of the vehicle spatial density, the average number of rebroadcast packets can be regulated by properly tuning a single parameter
Efficient broadcasting, through Irresponsible Forwarding, in intelligent transportation systems
No full textEfficient broadcasting in IEEE 802.11 networks through irresponsible forwarding
No full textIn a self-organizing vehicular network, vehicles share and distribute information by rebroadcasting a received information packet to their neighbors. An efficient broadcast technique can offer a high reactivity without sacrificing the communication reliability. Therefore, broadcast techniques are particularly suitable for safety-related vehicular transmissions, whose goal is reaching reliably the widest area in the shortest time. Among the numerous solutions appeared in the literature, the probabilistic broadcast approaches seem to be promising and not yet accurately analyzed. Since the interaction between a high level broadcasting protocol with the lower layers cannot be ignored, in this work we analyze the behavior of a recently proposed broadcast technique, denoted as the Irresponsible Forwarding (IF), in IEEE 802.11 networks. Our attention concentrates on the Medium Access Control (MAC) layer, which is affected by some critical impairments for broadcasting, such as the hidden terminal problem and self-interference. In this work, we evaluate the benefits brought by the use of IF to perform efficient broadcasting in IEEE 802.11 networks
Optimal transmit power in wireless sensor networks
No full textPower conservation is one of the most important issues in wireless ad hoc and sensor networks, where nodes are likely to rely on limited battery power. Transmitting at unnecessarily high power not only reduces the lifetime of the nodes and the network, but also introduces excessive interference. It is in the network designer’s best interest to have each node transmit at the lowest possible power while preserving network connectivity. In this paper, we investigate the optimal common transmit power, defined as the minimum transmit power used by all nodes necessary to guarantee network connectivity. This is desirable in sensor networks where nodes are relatively simple and it is difficult to modify the transmit power after deployment. The optimal transmit power derived in this paper is subject to the specific routing and medium access control (MAC) protocols considered; however, the approach can be extended to other routing and MAC protocols as well. In deriving the optimal transmit power, we distinguish ourselves from a conventional graph-theoretic approach by taking realistic physical layer characteristics into consideration. In fact, connectivity in this
paper is defined in terms of a quality of service (QoS) constraint given by the maximum tolerable bit error rate (BER) at the end of a multihop route with an average number of hops
Connectivity of ad hoc wireless networks: an alternative to graph-theoretic approaches
No full textConnectivity in wireless ad hoc and sensor networks is typically analyzed using a graph-theoretic approach. In this paper, we investigate an alternative communication-theoretic approach for determining the minimum transmit power required for achieving connectivity. Our results show that, if there is significant multipath fading and/or multiple access interference in the network, then graph theoretic approaches can substantially underestimate the minimum transmit power required for connectivity. This is due to the fact that graph-theoretic approaches do not take the route quality into consideration. Therefore, while in scenarios with line-of-sight (LOS) communications a graph-theoretic approach could be adequate for determining the minimum transmit power required for connectivity, in scenarios with strong multipath fading and/or multiple access interference a communication-theoretic approach could yield much more accurate results and, therefore, be preferable
Cluster-Based Irresponsible Forwarding
No full text"Proc. of the 20th Tyrrhenian International Workshop on Digital Communications" (Tyrrhenian 2009), Pula, Sardinia, Italy, September 200
Sensor networks with random versus uniform topology: MAC and interference considerations
No full textA new communication-theoretic framework for evaluating the performance of static ad hoc wireless networks (e.g., sensor networks) in terms of bit-error-rate (BER) has been introduced (Tonguz, O.K. and Ferrari, G., Carnegie Mellon University, ECE Dept., Tech. Rep. TR-043-2003, 2003; Ferrari and Tonguz, MILCOM, 2003; GLOBECOM, 2003); in it, for simplicity, it was assumed that the nodes lie at the vertices of a uniform square grid structure. Although this framework provides good insights into the performance of a sensor network, the square grid assumption makes it rather idealistic. In fact, the positions of nodes in a real sensor network are more likely to be random. We extend the framework to analyze the performance of an ad hoc wireless network with random topology, and we compare the obtained results with those obtained in the case of the uniform grid topology
Route reservation in ad hoc wireless networks
No full textThis paper investigates whether and when route reservation-based (RB) communication can yield better delay performance than non-reservation-based (NRB) communication in ad hoc wireless networks. In addition to posing this fundamental question, the requirements (in terms of route discovery, medium access control (MAC) protocol, and pipelining, etc.) for making RB switching superior to NRB switching are also identified. A novel analytical framework is developed and the network performance under both RB and NRB schemes is quantified. It is shown that if the aforementioned requirements are met, then RB schemes can indeed yield better delay performance than NRB schemes. This advantage, however, comes at the expense of lower throughput and goodput compared to NRB schemes
