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Vehicular ad hoc networks (VANETs) have been attracting interest for their potential roles in intelligent transport systems (ITS). In order to enable distributed ITS, there is a need to maintain some information in the vehicular networks without the support of any infrastructure such as road side units. In this paper, we propose a protocol that can store the data in VANETs by transferring data to a new carrier (vehicle) before the current data carrier is moving out of a specified region. For the next data carrier node selection, the protocol employs fuzzy logic to evaluate instant reward by taking into account multiple metrics, specifically throughput, vehicle velocity, and bandwidth efficiency. In addition, a reinforcement learning-based algorithm is used to consider the future reward of a decision. For the data collection, the protocol uses a cluster-based forwarding approach to improve the efficiency of wireless resource utilization. We use theoretical analysis and computer simulations to evaluate the proposed protocol. [ABSTRACT FROM AUTHOR]

We propose the low overhead media access control protocol (LO-MAC), a new low latency, energy efficient MAC protocol for low data rate wireless sensor networks. LO-MAC uses both duty cycling and multihop forwarding from the routing-enhanced MAC protocol (RMAC) to reduce idle listening and sleep latency, respectively. Besides that, LO-MAC introduces a traffic-adaptive mechanism, which is based on the fact that a node can sense a busy channel within its carrier sensing range. This mechanism uses carrier sensing as a binary signal, and effectively notifies nodes of the existence of a data packet. The nodes then either keep their radios on to take part in multihop data forwarding or turn them off to save energy. Moreover, LO-MAC takes full advantage of the broadcast nature of wireless communication and lets a packet have different meanings when it is in transmission range of different nodes. In LO-MAC, not only is a request-to-send/clear-to-send pair replaced with a Pioneer (PION) packet, as in RMAC, but also a data packet can play both data and acknowledgement functions. Therefore, control overhead and overhearing energy are significantly reduced. Our simulation results show that LO-MAC outperforms RMAC in terms of energy efficiency while achieving comparable end-to-end latency. [ABSTRACT FROM AUTHOR]

Abstract: Power efficiency and coverage preservation are two important performance metrics for a wireless sensor network. However, there is scarcely any protocol to consider them at the same time. In this paper, we propose a flow-balanced routing (FBR) protocol for multi-hop clustered wireless sensor networks that attempts to achieve both power efficiency and coverage preservation. The proposed protocol consists of four algorithms, one each for network clustering, multi-hop backbone construction, flow-balanced transmission, and rerouting. The proposed clustering algorithm groups several sensors into one cluster on the basis of overlapping degrees of sensors. The backbone construction algorithm constructs a novel multi-level backbone, which is not necessarily a tree, using the cluster heads and the sink. Furthermore, the flow-balanced routing algorithm assigns the transferred data over multiple paths from the sensors to the sink in order to equalize the power consumption of sensors. Lastly, the rerouting algorithm reconstructs the network topology only in a place where a head drops out from the backbone due to the head running out of its energy. Two metrics called the network lifetime and the coverage lifetime are used to evaluate the performance of FBR protocol in comparison with previous ones. The simulation results show that FBR yields both much longer lifetime and better coverage preservation than previous protocols. For example, FBR yields more than twice network lifetime and better coverage preservation than a previous efficient protocol, called the coverage-preserving clustering protocol (CPCP) [18], when the first sensor dies and the network coverage is kept at 100%, respectively. [Copyright &y& Elsevier]

A mobile ad hoc network (MANET) is a self-organized and adaptive wireless network formed by dynamically gathering mobile nodes. Since the topology of the network is constantly changing, the issue of routing packets and energy conservation become challenging tasks. In this paper, we propose a cross-layer design that jointly considers routing and topology control taking mobility and interference into account for MANETs. We called the proposed protocol as Mobility-aware Routing and Interference-aware Topology control (MRIT) protocol. The main objective of the proposed protocol is to increase the network lifetime, reduce energy consumption, and find stable end-to-end routes for MANETs. We evaluate the performance of the proposed protocol by comprehensively simulating a set of random MANET environments. The results show that the proposed protocol reduces energy consumption rate, end-to-end delay, interference while preserving throughput and network connectivity. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper address the energy conservation issues in wireless downlink of mobile networks with distributed antenna transmission. From the basic information theory for MIMO channels, we derived a simple energy efficiency defined as number of bits per Watt. we then identified three approaches to improve the optimal energy efficiency with a higher capacity, which include alleviating channel fading loss, mitigating the interference, and increasing the number of antennas. We considered the scenario of a single cell with distributed antennas to jointly investigate above three factors. We first proposed a beamforming based energy-efficient resource allocation algorithm, which can achieve the optimal energy efficiency with a higher capacity through adaptively allocating resources and managing interferences. Due to the computational complexity of this algorithm and real-time processing requirement, we further proposed a low-complexity antenna-selection based resource allocation algorithm, which is more tractable and only with slightly performance loss. Finally, we compared different network configurations with these algorithms by extensive simulations, the results demonstrate that the proposed algorithms in distributed antenna configurations achieve better energy efficiency at a high operational throughput point. [ABSTRACT FROM AUTHOR]

Energy harvesting technology potentially solves the problem of energy efficiency, which is the biggest challenge in wireless sensor networks. The sensor node, which has a capability of harvesting energy from the surrounding environment, is able to achieve infinitive lifetime. The technology promisingly changes the fundamental principle of communication protocols in wireless sensor networks. Instead of saving energy as much as possible, the protocols should guarantee that the harvested energy is equal to or bigger than the consumed energy. At the same time, the protocols are designed to have the efficient operation and maximum network performance. In this paper, we propose ERI-MAC, a new receiver-initiated MAC protocol for energy harvesting sensor networks. ERI-MAC leverages the benefit of receiver-initiated and packet concatenation to achieve good performance both in latency and in energy efficiency. Moreover, ERI-MAC employs a queueing mechanism to adjust the operation of a sensor node following the energy harvesting rate from the surrounding environment. We have extensively evaluated ERI-MAC in a large scale network with a realistic traffic model using the network simulator ns-2. The simulation results show that ERI-MAC achieves good network performance, as well as enabling infinitive lifetime of sensor networks. [ABSTRACT FROM AUTHOR]

As a promising way in surveillance applications, wireless sensor networks (WSNs) often encounter the target coverage (TC) problem, i.e., scheduling energy-limited sensors to monitor physical targets to prolong the network lifetime. Due to the complexity of the problem (scheduling in time domain), previous proposals mainly focus on heuristics and provable optimal algorithms remain unknown. In this paper, we fill in the research blank by providing several theoretical results. First, we present a mathematical formulation and several investigations of the problem in time domain. Such time-related results provide fundamental understandings of the problem and serve as a basis. Second, we offer an upper bound on the network lifetime derived from the time-dependant formulation. The bound, which is solvable in polynomial-time, serves as a performance benchmark. Third, we verify the set cover-based method, which is widely used by previous studies, via a transformation of the problem from time to space domain. Lastly, we offer a specialized nonlinear column generation (CG) based approach to solve the problem in space domain optimally. Simulation results show that not only the bound is effective, but also the CG-based approach offers significant improvement on the network lifetime over a brutal search algorithm and a state-of-art heuristic. [ABSTRACT FROM AUTHOR]