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In multi-interface multi-channel (MIMC) based tactical ad hoc networks, QoS support is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop...
In this paper, we discuss the challenges associated with integrating multiuser OFDMA in a single cell IEEE 802.11 based wireless ad hoc network and propose a new, dynamic and robust approach to improve it. Our new MAC, using OFDMA in the physical layer, can incorporate multiple concurrent transmissions or receptions in a dynamic manner and can adjust the collision probability based on the traffic...
An ad hoc network is a collection of wireless mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure or centralized administration. A number of routing protocols such as Dynamic Source Routing (DSR), Ad Hoc on-Demand Distance Vector Routing (AODV) and Destination-Sequenced Distance-Vector (DSDV) have been implemented. In this paper, an attempt has...
Supporting QoS for safety-critical applications for intelligent transportation systems accentuates the analytical modeling of delays in vehicular networks. Such analysis is, however, challenging due to the dynamics of such a network. We make progress by deriving lower- and upper-bounds for information dissemination delays in multi-hop vehicular networks using two different routing schemes. In particular,...
Recent advances in high-speed wireless LANs with physical layer (PHY) rates reaching 600Mbps make them ideal for multimedia applications. It has been shown that efficiency at medium access control (MAC) layer decreases with increasing the PHY rate. To achieve high efficiency, few researches have tried to use aggregation in which few packets are concatenated into a larger frame. The resultant frame...
We discuss protocols for all-to-all dissemination in ad-hoc wireless networks. We identify shortcomings and challenges related to high traffic and explore their causes by observing the performance at the MAC layer. Through simulations we show that a congestion assessment mechanism can reduce more than 1/4 of the traffic on a good part of the nodes without affecting dissemination performance. We conclude...
In this paper, we study the multi-channel exposed terminal problem in multi-hop wireless networks. We first explain how the multi-channel exposed terminal problem occurs. We then propose a multi-channel MAC protocol, called multi-channel MAC with hopping reservation (MMAC-HR), to resolve the multi-channel exposed terminal problem. The proposed MMAC-HR protocol has the following features: 1) it does...
In recent years, multi-channel MACs have attracted considerable attention in wireless networking research. Motivation for research into multi-channel MACs is their potential to increase the capacity of wireless ad hoc networks by exploiting multiple orthogonal frequency bands. This potential has been confirmed by several simulation studies that reported promising results for multi-channel MACs. However,...
Recently we proposed a cross-layer design to support video communication over error-prone mobile ad-hoc networks. The idea is to utilize routing messages and network parameters to estimate the corrupted frames, and to guide the reference frame selection at the video encoder to mitigate error propagation. In this paper, we focus on the frame corruption estimation method used in the design. We build...
Medium Access Control (MAC) delays significantly increase the packet service-time in saturated networks. As the number of contending nodes increases, the occurrence of collisions and cross-transmissions (CTs) also increases, resulting in high packet service-time. In this paper, we model packet servicetime in IEEE 802.11 Distributed Coordination Function (DCF) networks in terms of medium access delays,...
Intermittent connectivity is common in certain wireless access networks. Existing network protocols are not resilient to disruption of communication links and communication often fails when faced with sporadic connectivity. Thus in recent years there is a growing interest in Intermittently Connected Mobile Networks (also know as Mobile Opportunistic Networks) and many routing protocols have been proposed...
Nested Circular Directional MAC, a modified medium access control protocol of DMAC protocol, is proposed in this paper to support both directional antennas and omni-directional antennas simultaneously in one Ad Hoc network. Omni-directional antennas follow the RTS/CTS mechanism which is multi-hop and directional antennas follow the DRTS/DCTS mechanism, ensuring the asymmetric communication effectively...
Wireless ad-hoc networking will be a fundamental component of emerging technologies such as multi-hop cellular networks, vehicular ad-hoc networks and wireless mesh networks, with most of these technologies based on evolved versions of the 802.11 standard. To achieve their expected benefits, and address their challenges, in terms of energy efficiency, reliability or reconfigurability, advanced cooperative...
Congestion in mobile ad hoc networks not only results in transmission delay and packet loss, but also degrades throughput. For effective congestion detection and control, accurate estimation of MAC overhead, packet retransmission, backoff interval and queuing delay is necessary. This paper proposes a congestion aware nodes (CAN) based scheme to control congestion in mobile ad hoc networks. In this...
The performance of traditional TCP congestion control protocol degrades when congestion and contention increase in ad hoc networks that use the IEEE 802.11 DCF. Many of the problems result from medium contention at the media access control (MAC) layer. In this paper, we present a new contention-based congestion control (CBCC) method according to a novel congestion information from MAC layer. This...
In wireless multihop ad hoc networks, the hidden terminal problem severely degrades the overall performance. On the other hand, most existing solutions cause larger blocking areas and hence a more severe exposed-terminal problem. In this paper, we present a new Enhanced Busy-tone Multiple Access (EBTMA) medium access control (MAC) protocol. The proposed protocol minimizes the negative impact of both...
We consider the problem of designing cooperative driver assistance and collision warning systems in vehicular networks. In this problem each car has a small size state information message that should be received by its neighborhood within a short lifetime of L timeslots. Because of the safety nature of the application, communication reliability (success probability) and delay are of critical importance...
In order to become truly ubiquitous, the Internet of Things (IoT) has to evolve to provide connectivity anytime, any place, for any thing. IEEE 802.15.4-based wireless personal area networks (WPANs) is a preferable communication method for IoT. Wireless personal area networks (WPANs) are used to convey information over relatively short distances. Connections effected via WPANs involve little or no...
Delay-constrained video applications have stringent bandwidth, delay and loss requirements, which is a great challenge to support such real-time applications in wireless ad hoc networks. In this paper, to minimize the distortion of video received at the decoder, we propose a cross layer design (CLD) approach which combines the network layer and MAC layer to meet the stringent requirements by dynamically...
Multi-hop wireless ad hoc networks suffer from temporary link error due to fading. In order to improve packet transmission reliability and achieve efficient transmission in fading environment, this paper proposes an integrated dynamic multi-hopping scheme based on a cross-layer approach and cognitive behavior of local nodes. The scheme provides two important functions, temporary bypassing and dynamic...
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