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Unlike most IEEE 802.11-based ad hoc networks, in which only a single channel is used, wireless mesh networks allow the simultaneous use of multiple channels to increase the aggregated capacity. Many efforts have been taken to better exploit multiple non-overlapped channels. Although the IEEE 802.11 b/g standards, which govern the unlicensed 2.4 GHz industrial, scientific and medical (ISM) band, provide...
In wireless MIMO ad-hoc networks, channel reciprocity is assumed to optimize transmit and receive beamformers in conventional beamforming algorithms. But, when channels between nodes are not reciprocal, it is a huge burden to the feedback channel to inform a transmitting node of the channel state information. In this paper, we propose a distributed beamforming scheme with limited feedback for non-reciprocal...
The poor performance of TCP in multihop ad hoc networks is mainly attributed to the inefficient interaction among different protocol layers in previous literature, while the heavy load caused by end-to-end TCP acknowledgements (ACKs) with limited information is usually ignored. In this paper, we propose a novel incorporating ACK transfer scheme, IACK, to alleviate its impact. In IACK, TCP acknowledgements...
Medium access in ad-hoc wireless networks must be performed in a distributed fashion due to lack of coordination between nodes. Specifically, when nodes are capable of receiving more than one transmission simultaneously, the design of distributed medium-access mechanisms that efficiently exploit the receiver's capability becomes more challenging. Adaptive probabilistic medium access for ad-hoc wireless...
In this paper, we propose an adaptive forwarding scheme for achieving efficient message delivery in the mobile sensor delay-tolerant network (DTN). By adaptively adjusting the probability of replicating a message based on the information about the number of existing message copies in the network, the proposed scheme can achieve nice balance between the delivery delay and the average message copy....
In this paper, we propose a novel medium access control (MAC) protocol called flow-driven MAC (FD-MAC) for mobile ad hoc networks (MANETs). FD-MAC is a slotted MAC protocol that combines random access and reservation-based access, and introduces the concept of "data flow" and a flow-driven mechanism for resource reservation. For short-duration data flows, it employs a random access protocol,...
Due to the dynamic topology and non infrastructure, network participants cooperate with their neighbors to route packets. The lack of centralized services allows mobile ad hoc networks to be easily and swiftly deployed, but make it difficult to check others' identities on the other hand. Cryptographic tools have been introduced to secure group communications, such as private and public key infrastructure...
In this paper, we consider the energy-efficient resource allocation that minimizes a general cost function of average user powers in wireless networks. A class of so-called ??-fair cost functions is derived to balance the tradeoff between efficiency and fairness in energy-efficient designs. With these novel cost functions, optimal resource allocation schemes are developed for fading time-division...
It is possible for vehicles moving on a highway to communicate with each other, if they are equipped with wireless interfaces. These vehicles, equipped with wireless connectivity, are referred to as nodes in a Vehicular Ad Hoc Network (VANET). The more the number of nodes involved in a network at a time, the more is the power consumed by them, thereby adding to the average power consumption of the...
In this paper, we propose a new channel access protocol for transmission over cooperative ad-hoc networks. The proposed protocol, which aims at minimizing the number of blocked nodes and consequently improving the system throughput, employs directional antennas at both source and relay stations. The network performance under the proposed settings is modelled using continues Markov chains. Steady state...
In mobile ad hoc networks (MANETs), hierarchical key management structure has some distinct features and becomes popular in many applications. In a MANET where security requirement is high, node states should be considered when constructing a private key generator (PKG). In this paper, we propose a distributed hierarchical key management scheme in which nodes can get their keys updated from optimally...
Due to their nature, vehicular ad hoc network (VANET) is vulnerable to denial of service (DoS) attacks, such as jamming attack. The objective of a jammer is to interfere with legitimate wireless communications, and to degrade the overall QoS of the network. In this paper, we propose a model to detect a particular class of jamming attack, in which the jammer transmits only when valid radio activity...
The performance of prevalent MAC protocols in MANETs relies on the level of contention in networks. While contention-based MAC protocols such as CSMA suffer from inefficiency under high contention, slot-based MAC protocols such as TDMA perform in the opposite way. In this paper, we propose a hybrid protocol to which we refer as Load-Adaptive MAC (LA-MAC) protocol for MANETs. By adaptively switching...
In this paper we introduce a new MAC protocol called Continuous Contention-Assisted Transmission (CAT) for wireless Ad-hoc network. This proposed protocol is based on Carrier sense multiple access with collision avoidance (CSMA/CA) but we have modified the ACK packet and re-designed mobile stations behavior so that they could continuously transmit data without contention. Our proposed algorithm tries...
We study the scaling laws for wireless ad hoc network in which the distribution of nodes in the network is homogeneous but the traffic is heterogeneous. More specifically, we consider the case in which a node is the sink to k sources sending different information, while the rest of the nodes are part of unicast communications with a uniform assignment of source-destination pairs. We prove that the...
Clustering has been used as a fundamental tool to improve scalability in large wireless ad hoc networks. Techniques based on clustering, such as routing, self-organization, context management, service discovery, etc., ensure QoS in wireless ad hoc networks when the number of devices increases. The crucial issue of clustering is the overhead generated during the cluster formation and maintenance phases...
Network coding is a promising technology that can effectively improve the efficiency and capacity of multihop wireless networks by exploiting the broadcast nature of the wireless medium. However, current packet routing schemes do not take advantage of the network coding, and the benefits of network coding have not been fully utilized. To improve the performance gain of network coding, in this paper,...
In this paper, we present a spatiotemporal multicast, called a mobicast, protocol for supporting applications which require spatiotemporal coordination in VANETs. The spatiotemporal character of a mobicast is to forward a mobicast message to vehicles located in some geographic zone at time t, where the geographic zone is denoted as zone of relevance (ZOR). Vehicles located in ZOR at the time t must...
Multichannel wireless networks provide the flexibility to utilize the available spectrum efficiently for achieving improved system performance in terms of throughput and spectral efficiency. However, there has been no practical means for provisioning quality of service (QoS) in multichannel wireless networks. While previous proposals providing signaling and adaptation mechanisms for QoS, they support...
To achieve high safety levels in vehicular ad-hoc networks (VANETs), the Dedicated Short Range Communication (DSRC) implies each vehicle to periodically broadcast a safety beacon message. Many safety-related applications in VANET are based on the safety beacon messages. To ensure secure communications, the message authentication and integrity must be verified by respectively verifying the public key...
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