8,688 research outputs found

    The improvements in ad hoc routing and network performance with directional antennas

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    The ad hoc network has typically been applied in military and emergency environments. In the past decade, a tremendous amount of MAC protocols and routing protocols have been developed, but most of these protocols are designed for networks where devices equipped with omni-directional antennas. With fast development of the antenna technology, directional antennas have been proposed to improve routing and network performance in ad hoc networks. However, several challenges and design issues (like new hidden terminal problem, deafness problem, neighbor discovery problem and routing overhead problem) arise when applying directional antennas to ad hoc networks, consequently a great number of directional MAC and routing protocols have been proposed. In this thesis the implementation of directional antennas in ad hoc networks is studied from technical point of view. This thesis discusses the problems of utilizing directional antenna in ad hoc networks and reviews several recent proposed MAC algorithms and routing algorithms. The improvement of ad hoc routing and network performance with directional antennas compared with omni-directional antennas are evaluated based on simulations which are done with the QualNet simulator. The main finding of this study is that directional antennas always outperform omni-directional antennas in both static and mobility scenarios, and the advantage of directional antennas is more obvious when channel condition becomes worse or mobility level is larger. This thesis provides a survey of directional MAC and routing protocols in ad hoc networks. The result and principles obtained in this thesis are quite valuable for researchers working in this field. They can use it as reference for further researches. The theory parts of smart antenna technology and IEEE 802.11 MAC protocol can be considered as a technical introduction for beginners

    Channel-Access and Routing Protocols for Wireless Ad Hoc Networks with Directional Antennas

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    Medium-access control (MAC) and multiple-hop routing protocols are presented that exploit the presence of directional antennas at nodes in a wireless ad hoc network. The protocols are designed for heterogeneous networks in which an arbitrary subset use directional antennas. It is shown that the new protocols improvement the network`s performance substantially in a wide range of scenarios. A new MAC protocol is presented that employs the RTS/CTS mechanism. It accounts for the constraints imposed by a directional antenna system, and it is designed to exploit the capabilities of a directional antenna. It is shown that the receiver blocking problem is especially detrimental to the performance if the network includes nodes with directional antennas, and a simple solution is presented. A further improvement to the MAC protocol is presented which results in more efficient spatial reuse of traffic channels in the heterogeneous network. The protocol includes a mechanism by which a negotiating node pair dynamically determines if a traffic channel that is in use in the local area can be used concurrently to support additional traffic. It is shown that the new protocol yields significantly better performance than two existing approaches to the reuse of traffic channels. It is also shown that the improvements are achieved over a wide range of network conditions, including different network densities and different spread-spectrum processing gains. A new distributed routing protocol is also presented for use in heterogeneous wireless ad hoc networks. Two components of the routing protocol are jointly designed: a congestion-based link metric that identifies multiple routes with low levels of congestion, and a forwarding protocol that dynamically splits traffic among the multiple routes based on the relative capabilities of the routes. It is shown that the new routing protocol is able to exploit the decoupling of paths in the network resulting from the presence of nodes with directional antennas. Furthermore, it is shown that the protocol adapts effectively to the presence of advantaged nodes in the network. This approach to joint routing and forwarding is shown to result in a much better and more robust network performance than minimum-hop routing

    A Scalable Multicast Routing Protocol for Mobile Ad-Hoc Networks, Journal of Telecommunications and Information Technology, 2022, nr 2

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    The multicasting technique supports a variety of applications that require data to be instantaneously transmitted to a set of destination nodes. In environments with continuously moving nodes, such as mobile ad-hoc networks, the search for efficient routes from sources to the projected destinations is a common issue. Proposed Windmill protocol provides a scalable multicast solution for mobile ad-hoc networks. Windmill aims to improve routing protocol’s performance by introducing a hierarchal distributed routing algorithm and dividing the area into zones. Additionally, it attempts to demonstrate better scalability, performance and robustness when faced with frequent topology changes, by utilizing restricted directional flooding. A detailed and extensive simulated performance evaluation has been conducted to assess Windmill and compare it with multicast ad-hoc on-demand distance vector (MAODV) and on-demand multicast routing protocols (ODMRP). Simulation results show that the three protocols achieved high packet delivery rates in most scenarios. Results also show that Windmill is capable of achieving scalability by maintaining the minimum packet routing load, even upon increasing the nodes’ speed, the number of sources, the number of group members and the size of the simulated network. The results also indicate that it offers superior performance and is well suited for ad-hoc wireless networks with mobile hosts. The trade-off of using Windmill consists in slightly longer paths – a characteristic that makes it a good choice for applications that require simultaneous data transmission to a large set of nodes

    Energy Efficient Location Aided Routing Protocol for Wireless MANETs

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    A Mobile Ad-Hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without using any centralized access point, infrastructure, or centralized administration. In this paper we introduce an Energy Efficient Location Aided Routing (EELAR) Protocol for MANETs that is based on the Location Aided Routing (LAR). EELAR makes significant reduction in the energy consumption of the mobile nodes batteries by limiting the area of discovering a new route to a smaller zone. Thus, control packets overhead is significantly reduced. In EELAR a reference wireless base station is used and the network's circular area centered at the base station is divided into six equal sub-areas. At route discovery instead of flooding control packets to the whole network area, they are flooded to only the sub-area of the destination mobile node. The base station stores locations of the mobile nodes in a position table. To show the efficiency of the proposed protocol we present simulations using NS-2. Simulation results show that EELAR protocol makes an improvement in control packet overhead and delivery ratio compared to AODV, LAR, and DSR protocols.Comment: 9 Pages IEEE format, International Journal of Computer Science and Information Security, IJCSIS 2009, ISSN 1947 5500, Impact factor 0.423, http://sites.google.com/site/ijcsis
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