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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,...
In this paper we analyze the performance of a distributed queuing medium access control (MAC) protocol designed to execute cooperative ARQ (C-ARQ) schemes at the MAC layer. Due to the broadcast nature of the wireless channel, a user that receives a data packet with unrecoverable errors can request retransmission from any of the other users in the transmission range of the transmitter that overheard...
In this work, a new approach for dynamically allocating high priority probability and high priority slots in PR-ALOHA (Reserved ALOHA with Priority) was introduced. The Dynamic Slot Allocation (DSA) algorithm in PR-ALOHA is performed by dynamically allocating the number of high priority slots and high priority probability based on the available traffic. The performance of the system with DSA algorithm...
Efficient operation of a cognitive personal area network (CPAN) may be achieved if each data transmission is taxed by requiring the transmitting node to participate in cooperative sensing for a prescribed time period. We investigate the data transmission performance of this approach as well as its sensing accuracy. Through adaptive management of both the sensing process and data transmission, we show...
Cognitive radio networks enable opportunistic sharing of bandwidth/spectrum. In this paper, we propose a new Opportunistic Periodic MAC protocol (OP-MAC), a protocol that aims at improving the coexistence of licensed primary users and unlicensed secondary users in cognitive radio networks. Under OP-MAC, secondary users cooperate to periodically sense channels, report channel states and exchange control...
In this paper, a dynamic MAS reallocation method is proposed for the WiMedia MAC. WiMedia MAC configures a fully distributed network. WiMedia devices communicate during Superframe which is a communication unit in WiMedia MAC. guarantee QoS, WiMedia MAC uses a TDMA based time slot reservation protocol named distributed reservation protocol (DRP). On existing WiMedia networks, if any conflict occurs...
We propose and evaluate two retransmission-based schemes to improve the reliability of broadcasts in a contention-based MAC, with application to safety messages in dedicated short range communication (DSRC). These improve the reliability of event driven emergency messages without requiring feedback or additional protocol overhead. We also extend the Piggybacked ACK protocol into a feedback-based retransmission...
We develop a space-centric routing protocol to enable the delivery of mobile VoIP over high-mobility multi-hop wireless networks. The novel aspect of this protocol is the attribution of network and MAC layer congestion to space, which provides delay guarantees over much longer durations than can be achieved by node-centric routing protocols. The presented protocol constructs a spatial map of network...
This article addresses the problem of performance degradation of wireless sensor networks for scenarios involving data gathering to a small number of node sinks; as the data travel toward a sink, its neighbor nodes experience high loads and congestion. Using CSMA/CA as the basic access protocol, we implemented CoSenS, a collecting and sending burst scheme, on the top of it to address these issues...
In order to develop a contention-based MAC with quality of service (QoS) guarantee based on the distributed coordination function (DCF), we investigate the backoff scheme. We optimize the channel utilization with the constraint that delay requirement is guaranteed. Based on our analysis data, we propose the fixed contention window backoff (FCWB) scheme to get the best performance. The optimal performance...
A goal for next generation mobile networks is to provide seamless personal mobile communication and improved quality of service (QoS). Fair, class based service and lossless handoff are a focus for improving QoS. The research presented in this paper proposes a scheduling mechanism for providing improved QoS in mobile broadband Internet Protocol (IP) high-speed downlink packet access (HSDPA) networks...
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...
The spread use of wireless sensor networks (WSNs) in a variety of fields, ranging from the military to environmental protection, has drawn the attention of researchers to this type of networks. Despite their use in interesting applications, such as healthcare and surveillance, many shortcomings derived from their small size and constrained batteries limit their use, calling for solutions to enhance...
Wireless sensor networks typically conserve energy by following a periodic wakeup-sleep schedule: nodes minimize idle time and spend most of their time in a low power sleep state. In order to communicate and exchange data in such a network, the current duty-cycling MAC protocols either require tight synchronization between the neighbor wakeup schedules or spend a significant amount of energy in signaling...
The Mesh Coordinated Channel Access (MCCA) defined by the IEEE 802.11s draft standard implements a TDMA-based Medium Access Control (MAC) protocol by allowing mesh routers to negotiate collision-free transmission opportunities, called MCCAOPs, in a hop-by-hop manner. The procedure to determine the duration, in time slots, and the periodic schedule of MCCAOPs is however left unspecified by the standard...
Heterogeneous wireless network (HWN) technology enables a mobile client (MC) to access multiple heterogeneous subnets for better quality of service (QoS) at a lower cost. In the context of conventional network protocol, we cannot fully utilize the potential of a HWN by having separate and independently operating subnet interfaces. In this paper, we propose a multi-MAC management scheme, performing...
Surveillance and reconnaissance applications such as military in wireless sensor networks require timely transfer of important data (i.e., the detection of enemy troops and vehicles) to a remote base station or sink node. Unfortunately, picking up the reliable routing path to deliver the data in realtime is difficult because of various interferences, often environmental changes, and so on. Thus, routing...
To provide a more reliable link and deterministic delay for the mission-critical services, enhancement of the IEEE 802.15.4-2006 MAC specification was started in March 2008. The enhanced MAC specification offers three types of medium access control: Low Latency (LL), Time Slotted Channel Hopping (TSCH), and Distributed Synchronous Multi-Channel Extension (DSME). In this paper, the link access delay...
Polling schemes in the IEEE 802 MAC layer provide some QoS support for multimedia applications above what can be provided with the contention scheme. However, in highly loaded environments, reliability and efficiency remain the main challenges for current detailed polling schemes. In this paper, we present a detailed analysis of polling medium access, and propose a novel mechanism, the Registered...
We propose a simple unified analytical model to analyze the IEEE 802.11 DCF infrastructure BSS performance in terms of MAC delay, PLR, and throughput efficiency under non-homogeneous and non-saturation conditions. Our model accounts for: (i) asymmetric traffic load between an AP and its associated STAs of an infrastructure BSS; (ii) transition from the non-saturation to saturation mode (and vice-versa)...
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