1,720,967 research outputs found
Efficiency of Physical Carrier Sensing in Wireless Access Networks
No full textWe propose an analytical approach for evaluating the impact of physical carrier sensing in simple wireless access networks. We describe the system through a time-continuous Markov Chain, and we gather from its solution performance measures in terms of throughput and collision probability. We derive qualitative dimensioning criteria for the carrier sensing itself under different network conditions
Topology Control in Ad Hoc Netowrks: A MAC Layer Solution
No full textIn ad-hoc networks the need for a distributed topology control algorithm is being widely recognized. In this paper we propose TC-ADHOC MAC, a medium access algorithm with topology control capabilities. The proposed algorithm aims at maintaining the minimum number of bidirectional neighbors of any wireless terminal very close to a certain connectivity threshold. The correctness of the algorithm is evaluated through detailed simulation and several test on the impact of different algorithm parameters are carried out in static network scenarios. Furthermore, the ability of TC-ADHOC MAC of reusing the radio resources is assessed by a detailed simulation in a dynamic traffic environment. Our results show that the topology control solution integrated at the MAC layer helps increasing the channel reuse and, consequently, the network efficiency
Impact of user mobility on the broadcast service efficiency of the ADHOC MAC protocol
No full textWireless communication among vehicles is one of the hottest applications of ad hoc networking. The design and development of effective inter vehicles communication systems are key points to increase drivers safety through effective services like traffic monitoring and assistance, alarms signalling, etc. The ADHOC MAC for inter vehicle communications is a protocol recently developed within the CarTALK2000 project funded by the European Commission. In this paper we analyze its behavior and performance in scenarios where the users mobility is considered. Although the speed of the terminals poses stringent requirements on the network reconfiguration ability, the results obtained prove that the ADHOC MAC maintains good performances even considering terminals mobility
Directional Broadcast Forwarding of Alarm Messages in VANETs
No full textThe performance of general routing schemes for Vehicular Ad hoc NETworks (VANETs) is highly affected by the features of the specific Medium Access Control scheme the routing relies upon and by the mobility scenario. In this work, we address the design of position based routing solutions for the support of safety oriented applications in VANETs by focusing on the impact of the MAC layer on the performances of the routing strategies. Namely, we propose a simulation analysis in a realistic highway mobility scenario to assess the routing performance in the two cases where standard IEEE 802.11 technology and a dynamic TDMA scheme are adopted at layer 2 respectively. We discuss on the dimensioning of the routing parameters in both cases and we provide a comparative analysis of the two MAC/routing integrated solutions
SPARE MAC Enhanced: A Dynamic TDMA Protocol for Wireless Sensor Networks
No full textWireless Sensor Networks may support heterogeneous applications ranging from classical environmental monitoring, to more demanding integrated surveillance systems based on multimedia traffic. To this extent, we argue that the specific MAC layer solutions must be flexible enough to provide differentiated services based on the context of the specific WSN. In this work, we leverage the SPARE MAC protocol for WSN based on a receiver-oriented TDMA protocol, and we propose adaptive techniques to dynamically adjust the resource (slots) assignment which are able to track the changes in the network status (traffic increase/decrease, contention increase/decrease). We comment on the trade-off between performance gain and increased signalling complexity, by resorting to numerical results derived through simulation
Reuse Efficiency of Point-To-Point Connections in Ad Hoc Networks
No full textThe efficiency of Point-To-Point (PTP) connections in ad hoc networks highly depends on the capability of the Medium Access Control (MAC) layer to reuse the shared wireless resource. One of the most critical impairments to the reuse capability is the exposed terminal problem which may prevent feasible PTP communications to run in parallel. In this paper we evaluate the impact of the exposed terminal on the reuse efficiency of PTP communications in ad hoc random networks. To this end, we propose a scheduling algorithm for PTP connections within the framework of ADHOC MAC, a recently proposed MAC scheme. The simulative results we gather show that the solution of the exposed terminal problem provides a reuse efficiency gain around the 40% in the network scenario we considered
Evaluation of Integrated Routing/MAC Solutions for the Diffusion of Warning Messages in
No full textAbstract — The efficiency of routing protocols in general mobile ad hoc networks may be highly affected by the specific Medium Access Control scheme the routing relies upon and by the mobility of the wireless nodes. In this work, we address the design of position based routing solutions for the support of safety oriented applications in Vehicular Ad hoc NETworks (VANETs) by focusing on the impact of the MAC layer on the performances of the routing strategies. Namely, we propose a simulation analysis in highway scenarios to assess the routing performance in the two cases where standard IEEE 802.11 technology and a dynamic TDMA scheme are adopted at layer 2 respectively. We discuss on the dimensioning of the routing parameters in both cases and we provide a comparative analysis of the two MAC/routing integrated solutions. Index Terms — VANETs, geographical routing, Safety Applications I
A Cross-Layer Solution for Ultrawideband Based Wireless Video Sensor Networks
No full textA cross-layer communication protocol called VSN-module is introduced for wireless video sensor networks based on ultrawideband (UWB) radio technology at the physical layer. The core of our solution is a distributed path reservation scheme which routes video traffic from sources (sensors) to a sink. The path establishment takes into account the specific requirements of video flows such as bandwidth, end-to-end delay and jitter, as well as the current status of the traversed devices such as the available bandwidth, the energy consumption, and the quality of the wireless channels. Simulation experiments are carried out and the performance of the VSN-module is evaluated in terms of maximum end-to-end delivery delay, maximum delay jitter, and power consumption, under different video flow requirements
A Receiver Oriented MAC Protocol for Wireless Sensor Networks
No full textIn this paper we propose SPARE MAC, a TDMA based medium access control (MAC) scheme for data diffusion in Wireless Sensor Networks (WSNs). The rationale behind SPARE MAC is to spare energy through limiting the impact of idle listening and traffic overhearing. To this extent, SPARE MAC implements a distributed scheduling solution which assigns to each sensor specific radio resources (i.e., time slots) for reception, summarized as Reception Schedules (RS), and spreads the information of the assigned RS to neighboring sensors. A transmitting sensor can consequently become active in correspondence of the RS of its intended receiver only. We analyze the performance of SPARE MAC in terms of throughput, power consumption, and data delivery delay both through analytical models and through detailed simulations. Moreover, we compare the performance of SPARE MAC against SMAC
Performance Evaluation of point-to-point scheduling strategies for the ADHOC MAC protocol
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