Current Issue : October - December Volume : 2015 Issue Number : 4 Articles : 5 Articles
Periodical broadcasts of individual vehicle�s safety information such as velocity and acceleration are critical in vehicular ad\nhoc networks (VANETs). However, current contention-based media access control (MAC) protocols cannot guarantee high\nperformance in high density VANETs. In this paper, we propose a MAC protocol based on s-disjunct code to achieve reliable and\nreal-time broadcasts via assigning a channel to each vehicle as the vehicle enters the network. Our protocol is adaptive as vehicles are\nrequired to adjust their communication ranges according to the network density in order to avert the interference among them.We\nconduct an extensive simulation study, and our results indicate that the proposed scheme can successfully achieve the requirements\nof the dedicated short range communication (DSRC) standard, that is, to broadcast safety information 10 times per second. Even at\na high vehicle density, our scheme still guarantees that the success rates of both transmission and reception are greater than 95%,\nand the collision rates of access collision and merging collision are lower than 10 collisions/period....
Considering the limited resources and the dynamic spectrum distribution in the cognitive radio sensor networks (CRSN), a half duplex\nMultichannel broadcast protocol for CRSN is presented based on the home channel. This protocol maintains the networks\ntopology only through the home channel, so there is no need for the public channel to transmit the control information and no\nneed for the synchronization. After network initialization, node broadcasts data via home channel in half-duplex transmission way.\nThe simulation results show that, compared with complete broadcast, the proposed protocol effectively reduces broadcast delay and\noverhead....
Broadcast has critical significance for wide application of wireless sensor networks (WSNs). Minimum-latency broadcast (MLB)\nstudies how to devise a broadcast schedule, which can achieve minimum broadcast latency with no signal interference. In\nmultichannel duty-cycled WSNs, nodes can exploit multiple channels to communicate and periodically fall asleep after working\nfor some time. Nevertheless, most solutions to the MLB problem either focus on nonsleeping scenarios or only exploit one single\nchannel. Therefore, we investigate the MLB problem in multichannel duty-cycled WSNs in this paper and call this problem as\nMLBCD problem. We prove that MLBCD problem is NP-hard. We propose a new concept of active interference graph (AIG).\nBased on AIG, we present one novel approximation broadcast algorithm called NAB to solve the MLBCD problem.We prove that\nour proposed NAB algorithm achieves provable performance guarantee. The results of our extensive evaluations show that NAB\nalgorithm can significantly improve the broadcast latency....
Abstract As the use of wireless sensor networks increases, the need for efficient and\nreliable broadcasting algorithms grows. Ideally, a broadcasting algorithm should have\nthe ability to quickly disseminate data, while keeping the number of transmissions low.\nIn this paper, we analyze the popular Trickle algorithm, which has been proposed as\na suitable communication protocol for code maintenance and propagation in wireless\nsensor networks. We show that the broadcasting process of a network using Trickle\ncan be modeled by a Markov chain and that this chain falls under a class of Markov\nchains, closely related to residual lifetime distributions. It is then shown that this class\nof Markov chains admits a stationary distribution of a special form. These results\nare used to analyze the Trickle algorithm and its message count. Our results prove\nconjectures made in the literature concerning the effect of a listen-only period. Besides\nproviding a mathematical analysis of the algorithm, we propose a generalized version\nof Trickle, with an additional parameter defining the length of a listen-only period....
A vehicular ad hoc network (VANET) could deliver safety-related messages reliably within a short time to increase road safety.\nSince safety-related messages should be sent to a set of unspecified receivers, they are delivered by broadcast method. However, the\nbroadcast method specified in the IEEE 802.11p does not have a collision avoidance procedure and receivers do not acknowledge\nwhen they receive a broadcast frame. In addition, frames could be lost and corrupted. Therefore, as the portion of nodes that do not\nreceive a broadcast frame increases, the effectiveness of a safety application decreases. To tackle the problem, we propose a reliable\nand swift message broadcast method (RSMB). In RSMB, to expedite message dissemination process, a relay node is selected in a\ndistributed manner considering the progress made to a frame and the delay requirements of an application. In addition, a relay\nnode broadcasts a message multiple times to assure that the probability that the other nodes successfully receive the message at\nleast once is larger than a given threshold value. Since the number of rebroadcasts is regulated based on the successful message\nreception probability, the additional bandwidth needed to increase the reliability of broadcast is reasonably small....
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