The Experts below are selected from a list of 12780 Experts worldwide ranked by ideXlab platform
Nitin H. Vaidya - One of the best experts on this subject based on the ideXlab platform.
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on designing mac protocols for wireless networks using Directional Antennas
IEEE Transactions on Mobile Computing, 2006Co-Authors: Romit Roy Choudhury, Ram Ramanathan, Xue Yang, Nitin H. VaidyaAbstract:We investigate the possibility of using Directional Antennas for medium access control in wireless ad hoc networks. Previous research in ad hoc networks typically assumes the use of omniDirectional Antennas at all nodes. With omniDirectional Antennas, while two nodes are communicating using a given channel, MAC protocols such as IEEE 802.11 require all other nodes in the vicinity to remain silent. With Directional Antennas, two pairs of nodes located in each other's vicinity may potentially communicate simultaneously, increasing spatial reuse of the wireless channel. Range extension due to higher gain of Directional Antennas can also be useful in discovering fewer hop routes. However, new problems arise when using Directional beams that simple modifications to 802.11 may not be able to mitigate. This paper identifies these problems and evaluates the tradeoffs associated with them. We also design a Directional MAC protocol (MMAC) that uses multihop RTSs to establish links between distant nodes and then transmits CTS, DATA, and ACK over a single hop. While MMAC does not address all the problems identified with Directional communication, it is an attempt to exploit the primary benefits of beamforming in the presence of some of these problems. Results show that MMAC can perform better than IEEE 802.11, although we find that the performance is dependent on the topology and flow patterns in the system.
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performance of ad hoc routing using Directional Antennas
Ad Hoc Networks, 2005Co-Authors: Romit Roy Choudhury, Nitin H. VaidyaAbstract:This paper evaluates the tradeoffs involved in using Directional Antennas in ad hoc routing. Although problems with utilizing Directional Antennas have been visited in the past, the research has been confined mostly to medium access control. To determine whether Directional Antennas are beneficial to ad hoc networks, it is necessary to evaluate the impact of Directional Antennas on the performance of routing protocols as well. In this paper, we evaluate the performance of DSR (dynamic source routing) using Directional Antennas. We identify several issues that emerge from executing DSR (originally designed for omniDirectional Antennas) over Directional Antennas. Using insights gained from simulations, we propose routing strategies that adapt the routing protocol to Directional communication. Our analysis shows that by using Directional Antennas, ad hoc networks may achieve better performance. However, scenarios exist in which using omniDirectional Antennas may be more appropriate.
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impact of Directional Antennas on ad hoc routing
Lecture Notes in Computer Science, 2003Co-Authors: Romit Roy Choudhury, Nitin H. VaidyaAbstract:Previous research on Directional Antennas has been confined mostly to medium access control. However, it is necessary to evaluate the impact of Directional Antennas on the performance of routing protocols as well. In this paper, we identify the issues and evaluate the performance of an omniDirectional routing protocol, DSR, when executed over Directional Antennas. Using insights gained from simulations, we propose routing strategies suitable for Directional communication. Our analysis shows that by using Directional Antennas, ad hoc networks may achieve better performance. However, scenarios exist in which omniDirectional Antennas may be suitable.
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PWC - Impact of Directional Antennas on Ad Hoc Routing
Lecture Notes in Computer Science, 2003Co-Authors: Romit Roy Choudhury, Nitin H. VaidyaAbstract:Previous research on Directional Antennas has been confined mostly to medium access control. However, it is necessary to evaluate the impact of Directional Antennas on the performance of routing protocols as well. In this paper, we identify the issues and evaluate the performance of an omniDirectional routing protocol, DSR, when executed over Directional Antennas. Using insights gained from simulations, we propose routing strategies suitable for Directional communication. Our analysis shows that by using Directional Antennas, ad hoc networks may achieve better performance. However, scenarios exist in which omniDirectional Antennas may be suitable.
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using Directional Antennas for medium access control in ad hoc networks
ACM IEEE International Conference on Mobile Computing and Networking, 2002Co-Authors: Romit Roy Choudhury, Ram Ramanathan, Xue Yang, Nitin H. VaidyaAbstract:Previous research in wireless ad hoc networks typically assumes the use of omniDirectional Antennas at all nodes. With omniDirectional Antennas, while two nodes are communicating using a given channel, MAC protocols such as IEEE 802.11 require all other nodes in the vicinity to stay silent. With Directional Antennas, two pairs of nodes located in each other's vicinity may potentially communicate simultaneously, depending on the directions of transmission. This can increase spatial reuse of the wireless channel. In addition, the higher gain of Directional Antennas allows a node to communicate with other nodes located far away, implying that messages could be delivered to the destination in fewer hops. In this paper, we propose a MAC protocol that exploits the characteristics of Directional Antennas. Our design focuses on using multi-hop RTSs to establish links between distant nodes, and then transmit CTS, DATA and ACK over a single hop. Results show that our Directional MAC protocol can perform better than IEEE 802.11, although we find that the performance is dependent on the topology configuration and the flow patterns in the system.
Minyou Wu - One of the best experts on this subject based on the ideXlab platform.
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Channel Allocation in Wireless Networks with Directional Antennas
Journal of Sensor and Actuator Networks, 2013Co-Authors: Kam-wing Ng, Minyou WuAbstract:In this paper, we study the channel allocation in multi-channel wireless ad hoc networks with Directional Antennas. In particular, we investigate the problem: given a set of wireless nodes equipped with Directional Antennas, how many channels are needed to ensure collision-free communications? We derive the upper bounds on the number of channels, which heavily depend on the node density and the interference ratio (i.e., the ratio of the interference range to the transmission range). We construct several scenarios to examine the tightness of the derived bounds. We also take the side-lobes and back-lobes as well as the signal path loss into our analysis. Our results can be used to estimate the number of channels required for a practical wireless network (e.g., wireless sensor network) with Directional Antennas.
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an overview of using Directional Antennas in wireless networks
International Journal of Communication Systems, 2013Co-Authors: Kam-wing Ng, Minglu Li, Minyou WuAbstract:SUMMARY Compared with omni-Directional Antennas, Directional Antennas have many merits, such as lower interference, better spatial reuse, longer transmission range, and improved network capacity. Directional Antennas enable numerous emerging outdoor and indoor applications, which have been addressed in many recent studies. Despite the advances in wireless networks with Directional Antennas (DAWNs), there are many research challenges in all layers of DAWNs. This paper presents a detailed study on recent advances and open research issues on DAWNs. Firstly, we briefly introduce the classification of Directional Antennas, antenna radiation patterns, antenna modes, and the challenges in the physical layer of DAWNs. We then present research issues on the medium access control (MAC) layer, followed by the current solutions as well as open research problems on the MAC layer of DAWNs. In addition, we also discuss the research issues on the routing layer and the transport layer. Moreover, other research challenges on the performance evaluation of DAWNs and a brief introduction of indoor DAWNs are given in this paper as well. In conclusion, we summarize the current research issues on DAWNs as well as prospects in the future. Copyright © 2011 John Wiley & Sons, Ltd.
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on the capacity of multi channel wireless networks using Directional Antennas
International Conference on Computer Communications, 2008Co-Authors: Kam-wing Ng, Raymond Chi-wing Wong, Minyou WuAbstract:The capacity of wireless ad hoc networks is affected by two key factors: the interference among concurrent transmissions and the number of simultaneous transmissions on a single interface. Recent studies found that using multiple channels can separate concurrent transmissions and greatly improve network throughput. However, those studies only consider that wireless nodes are equipped with only omniDirectional Antennas, which cause high collisions. On the other hand, some researchers found that Directional Antennas bring more benefits such as reduced interference and increased spatial reuse compared with omniDirectional Antennas. But, they only focused on a single-channel network which only allows finite concurrent transmissions. Thus, combining the two technologies of multiple channels and Directional Antennas together potentially brings more benefits. In this paper, we propose a multi-channel network architecture (called MC-MDA) that equips each wireless node with multiple Directional Antennas. We derive the capacity bounds of MC-MDA networks under arbitrary and random placements. We will show that deploying Directional Antennas to multi-channel networks can greatly improve the network capacity due to increased network connectivity and reduced interference. We have also found that even a multi-channel network with a single Directional antenna only at each node can give a significant improvement on the throughput capacity. Besides, using multiple channels mitigates interference caused by Directional Antennas. MC-MDA networks integrate benefits from multi-channel and Directional Antennas and thus have significant performance improvement.
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INFOCOM - On the Capacity of Multi-Channel Wireless Networks Using Directional Antennas
IEEE INFOCOM 2008 - The 27th Conference on Computer Communications, 2008Co-Authors: Kam-wing Ng, Raymond Chi-wing Wong, Minyou WuAbstract:The capacity of wireless ad hoc networks is affected by two key factors: the interference among concurrent transmissions and the number of simultaneous transmissions on a single interface. Recent studies found that using multiple channels can separate concurrent transmissions and greatly improve network throughput. However, those studies only consider that wireless nodes are equipped with only omniDirectional Antennas, which cause high collisions. On the other hand, some researchers found that Directional Antennas bring more benefits such as reduced interference and increased spatial reuse compared with omniDirectional Antennas. But, they only focused on a single-channel network which only allows finite concurrent transmissions. Thus, combining the two technologies of multiple channels and Directional Antennas together potentially brings more benefits. In this paper, we propose a multi-channel network architecture (called MC-MDA) that equips each wireless node with multiple Directional Antennas. We derive the capacity bounds of MC-MDA networks under arbitrary and random placements. We will show that deploying Directional Antennas to multi-channel networks can greatly improve the network capacity due to increased network connectivity and reduced interference. We have also found that even a multi-channel network with a single Directional antenna only at each node can give a significant improvement on the throughput capacity. Besides, using multiple channels mitigates interference caused by Directional Antennas. MC-MDA networks integrate benefits from multi-channel and Directional Antennas and thus have significant performance improvement.
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an overview of mac protocols with Directional Antennas in wireless ad hoc networks
International Multi-Conference on Computing in Global Information Technology, 2006Co-Authors: Kam-wing Ng, Minyou WuAbstract:Although Directional Antennas have been used in mobile communications systems for quite a long time, realistic applications of Directional or smart Antennas in wireless ad hoc network have emerged just in recent years. Directional Antennas provide numerous benefits, such as higher gains, increased transmission range and low interferences. Wireless medium access schemes play a crucial role in ensuring the efficient and fair sharing of wireless resources. Therefore there are many research work on mechanisms at the wireless medium access layer by using Directional Antennas. The new features of MAC with Directional Antennas can cause not only location dependent carrier sensing problems, which have appeared in omniDirectional wireless networks, but also novel issues related to Directional Antennas. In this paper, an introduction of Directional Antennas is given. We give a classification of the current wireless MAC protocols using Directional Antennas. We also present different MAC protocols and compare them. This survey discusses the challenges in the design of these MAC protocols.
Kam-wing Ng - One of the best experts on this subject based on the ideXlab platform.
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Collision avoidance mechanisms in multi-channel wireless networks using Directional Antennas
2020Co-Authors: Kam-wing NgAbstract:The capacity of wireless networks are mainly affected by two key factors: the interference among concurrent transmissions and the number of simultaneous transmissions on a single interface. Recent studies have found that, using multiple channels can separate concurrent transmissions and significantly improve network throughput. However, those studies only consider wireless nodes that are only equipped with omni-Directional Antennas, which cause high collisions. On the other hand, some researchers have found that Directional Antennas bring more benefits such as the reduced interference and the increased spatial reuse compared with omni-Directional Antennas. But, they only focused on a single-channel network which only allows finite concurrent transmissions. In this thesis, we propose a novel network architecture, in terms of multi-channel networks using multiple Directional Antennas ( MC-MDA), which integrates the two technologies of multiple channels and Directional Antennas together and potentially brings more benefits. We study the capacity of MC-MDA networks and explore the benefits of such networks. We have found that using Directional Antennas in multi-channel networks can greatly increase the network capacity. Furthermore, such networks require fewer channels than multi-channels with omni-Directional Antennas. More specifically, we study the channel assignment problem of such MC-MDA networks. Our results indicate that using Directional Antennas in wireless networks can significantly reduce the required number of channels. Directional Antennas have a better spectrum reuse than omni-Directional Antennas. However, applying Directional Antennas to wireless networks can also cause new collisions, such as the new hidden terminal problem and the deafness problem. We study the challenges in the MAC layer design with Directional Antennas and present the state of the art of current MAC protocols with Directional Antennas. Then, we propose a novel collision avoidance scheme in terms of BT-DMAC (Busy-Tone based Directional Medium Access Control) to address the new collisions with Directional Antennas. Both the analytical and simulation results show that transmitting busy tones on a different channel can effectively reduce the hidden nodes and mitigate the deafness problem. Thus, integrating multiple channels with Directional Antennas can bring numerous benefits. Furthermore, we also explore some techniques in the MAC layer design with Directional Antennas. Some useful insights are also given.
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Channel Allocation in Wireless Networks with Directional Antennas
Journal of Sensor and Actuator Networks, 2013Co-Authors: Kam-wing Ng, Minyou WuAbstract:In this paper, we study the channel allocation in multi-channel wireless ad hoc networks with Directional Antennas. In particular, we investigate the problem: given a set of wireless nodes equipped with Directional Antennas, how many channels are needed to ensure collision-free communications? We derive the upper bounds on the number of channels, which heavily depend on the node density and the interference ratio (i.e., the ratio of the interference range to the transmission range). We construct several scenarios to examine the tightness of the derived bounds. We also take the side-lobes and back-lobes as well as the signal path loss into our analysis. Our results can be used to estimate the number of channels required for a practical wireless network (e.g., wireless sensor network) with Directional Antennas.
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an overview of using Directional Antennas in wireless networks
International Journal of Communication Systems, 2013Co-Authors: Kam-wing Ng, Minglu Li, Minyou WuAbstract:SUMMARY Compared with omni-Directional Antennas, Directional Antennas have many merits, such as lower interference, better spatial reuse, longer transmission range, and improved network capacity. Directional Antennas enable numerous emerging outdoor and indoor applications, which have been addressed in many recent studies. Despite the advances in wireless networks with Directional Antennas (DAWNs), there are many research challenges in all layers of DAWNs. This paper presents a detailed study on recent advances and open research issues on DAWNs. Firstly, we briefly introduce the classification of Directional Antennas, antenna radiation patterns, antenna modes, and the challenges in the physical layer of DAWNs. We then present research issues on the medium access control (MAC) layer, followed by the current solutions as well as open research problems on the MAC layer of DAWNs. In addition, we also discuss the research issues on the routing layer and the transport layer. Moreover, other research challenges on the performance evaluation of DAWNs and a brief introduction of indoor DAWNs are given in this paper as well. In conclusion, we summarize the current research issues on DAWNs as well as prospects in the future. Copyright © 2011 John Wiley & Sons, Ltd.
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on the capacity of multi channel wireless networks using Directional Antennas
International Conference on Computer Communications, 2008Co-Authors: Kam-wing Ng, Raymond Chi-wing Wong, Minyou WuAbstract:The capacity of wireless ad hoc networks is affected by two key factors: the interference among concurrent transmissions and the number of simultaneous transmissions on a single interface. Recent studies found that using multiple channels can separate concurrent transmissions and greatly improve network throughput. However, those studies only consider that wireless nodes are equipped with only omniDirectional Antennas, which cause high collisions. On the other hand, some researchers found that Directional Antennas bring more benefits such as reduced interference and increased spatial reuse compared with omniDirectional Antennas. But, they only focused on a single-channel network which only allows finite concurrent transmissions. Thus, combining the two technologies of multiple channels and Directional Antennas together potentially brings more benefits. In this paper, we propose a multi-channel network architecture (called MC-MDA) that equips each wireless node with multiple Directional Antennas. We derive the capacity bounds of MC-MDA networks under arbitrary and random placements. We will show that deploying Directional Antennas to multi-channel networks can greatly improve the network capacity due to increased network connectivity and reduced interference. We have also found that even a multi-channel network with a single Directional antenna only at each node can give a significant improvement on the throughput capacity. Besides, using multiple channels mitigates interference caused by Directional Antennas. MC-MDA networks integrate benefits from multi-channel and Directional Antennas and thus have significant performance improvement.
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INFOCOM - On the Capacity of Multi-Channel Wireless Networks Using Directional Antennas
IEEE INFOCOM 2008 - The 27th Conference on Computer Communications, 2008Co-Authors: Kam-wing Ng, Raymond Chi-wing Wong, Minyou WuAbstract:The capacity of wireless ad hoc networks is affected by two key factors: the interference among concurrent transmissions and the number of simultaneous transmissions on a single interface. Recent studies found that using multiple channels can separate concurrent transmissions and greatly improve network throughput. However, those studies only consider that wireless nodes are equipped with only omniDirectional Antennas, which cause high collisions. On the other hand, some researchers found that Directional Antennas bring more benefits such as reduced interference and increased spatial reuse compared with omniDirectional Antennas. But, they only focused on a single-channel network which only allows finite concurrent transmissions. Thus, combining the two technologies of multiple channels and Directional Antennas together potentially brings more benefits. In this paper, we propose a multi-channel network architecture (called MC-MDA) that equips each wireless node with multiple Directional Antennas. We derive the capacity bounds of MC-MDA networks under arbitrary and random placements. We will show that deploying Directional Antennas to multi-channel networks can greatly improve the network capacity due to increased network connectivity and reduced interference. We have also found that even a multi-channel network with a single Directional antenna only at each node can give a significant improvement on the throughput capacity. Besides, using multiple channels mitigates interference caused by Directional Antennas. MC-MDA networks integrate benefits from multi-channel and Directional Antennas and thus have significant performance improvement.
Hao Wang - One of the best experts on this subject based on the ideXlab platform.
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WCNC - Improvement of Multi-Channel MAC Protocol for Dense VANET with Directional Antennas
2009 IEEE Wireless Communications and Networking Conference, 2009Co-Authors: Furong Wang, Kewei Li, Peng Zhang, Hao WangAbstract:Directional Antennas in Ad hoc networks offer more benefits than the traditional Antennas with omni-Directional mode. With Directional Antennas, it can increase the spatial reuse of the wireless channel. A higher gain of Directional Antennas makes terminals a further transmission range and fewer hops to the destination. This paper presents the design, implementation and simulation results of a multi-channel Medium Access Control (MAC) protocols for dense Vehicular Ad hoc Networks using Directional Antennas with local beam tables. Numeric results show that our protocol performs better than the existing multichannel protocols in vehicular environment.
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improvement of multi channel mac protocol for dense vanet with Directional Antennas
Wireless Communications and Networking Conference, 2009Co-Authors: Furong Wang, Kewei Li, Peng Zhang, Hao WangAbstract:Directional Antennas in Ad hoc networks offer more benefits than the traditional Antennas with omni-Directional mode. With Directional Antennas, it can increase the spatial reuse of the wireless channel. A higher gain of Directional Antennas makes terminals a further transmission range and fewer hops to the destination. This paper presents the design, implementation and simulation results of a multi-channel Medium Access Control (MAC) protocols for dense Vehicular Ad hoc Networks using Directional Antennas with local beam tables. Numeric results show that our protocol performs better than the existing multichannel protocols in vehicular environment.
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Adaptive Multi-channel MAC Protocol for Dense VANET Using Directional Antennas
2008 Second International Conference on Future Generation Communication and Networking, 2008Co-Authors: Xu Xie, Furong Wang, Hao Wang, Kewei LiAbstract:Directional Antennas can increase the spatial reuse of the wireless channels and reach a higher antenna gain. This paper presents the design, implementation and simulation results of a multi-channel medium access control protocols for high density vehicular ad hoc networks using Directional Antennas with local beam tables. Simulation shows that our protocol has a higher throughput than the existing multi-channel protocols.
Ram Ramanathan - One of the best experts on this subject based on the ideXlab platform.
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on designing mac protocols for wireless networks using Directional Antennas
IEEE Transactions on Mobile Computing, 2006Co-Authors: Romit Roy Choudhury, Ram Ramanathan, Xue Yang, Nitin H. VaidyaAbstract:We investigate the possibility of using Directional Antennas for medium access control in wireless ad hoc networks. Previous research in ad hoc networks typically assumes the use of omniDirectional Antennas at all nodes. With omniDirectional Antennas, while two nodes are communicating using a given channel, MAC protocols such as IEEE 802.11 require all other nodes in the vicinity to remain silent. With Directional Antennas, two pairs of nodes located in each other's vicinity may potentially communicate simultaneously, increasing spatial reuse of the wireless channel. Range extension due to higher gain of Directional Antennas can also be useful in discovering fewer hop routes. However, new problems arise when using Directional beams that simple modifications to 802.11 may not be able to mitigate. This paper identifies these problems and evaluates the tradeoffs associated with them. We also design a Directional MAC protocol (MMAC) that uses multihop RTSs to establish links between distant nodes and then transmits CTS, DATA, and ACK over a single hop. While MMAC does not address all the problems identified with Directional communication, it is an attempt to exploit the primary benefits of beamforming in the presence of some of these problems. Results show that MMAC can perform better than IEEE 802.11, although we find that the performance is dependent on the topology and flow patterns in the system.
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ad hoc networking with Directional Antennas a complete system solution
IEEE Journal on Selected Areas in Communications, 2005Co-Authors: Ram Ramanathan, Jason Keith Redi, C Santivanez, David P Wiggins, S PolitAbstract:Directional Antennas offer tremendous potential for improving the performance of ad hoc networks. Harnessing this potential, however, requires new mechanisms at the medium access and network layers for intelligently and adaptively exploiting the antenna system. While recent years have seen a surge of research into such mechanisms, the problem of developing a complete ad hoc networking system, including the unique challenge of real-life prototype development and experimentation has not been addressed. In this paper, we present utilizing Directional Antennas for ad hoc networking (UDAAN). UDAAN is an interacting suite of modular network- and medium access control (MAC)-layer mechanisms for adaptive control of steered or switched antenna systems in an ad hoc network. UDAAN consists of several new mechanisms-a Directional power-controlled MAC, neighbor discovery with beamforming, link characterization for Directional Antennas, proactive routing and forwarding-all working cohesively to provide the first complete systems solution. We also describe the development of a real-life ad hoc network testbed using UDAAN with switched Directional Antennas, and we discuss the lessons learned during field trials. High fidelity simulation results, using the same networking code as in the prototype, are also presented both for a specific scenario and using random mobility models. For the range of parameters studied, our results show that UDAAN can produce a very significant improvement in throughput over omniDirectional communications.
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ad hoc networking with Directional Antennas a complete system solution
Wireless Communications and Networking Conference, 2004Co-Authors: Ram Ramanathan, Jason Keith Redi, C Santivanez, David P Wiggins, S PolitAbstract:In this paper, we present UDAAN ("utilizing Directional Antennas for ad hoc networking"), which is an interacting suite of modular network- and MAC-layer mechanisms for adaptive control of steered or switched antenna systems in an ad hoc network. UDAAN consists of several new mechanisms - a Directional power-controlled MAC, neighbor discovery with beamforming, link characterization with Directional Antennas, proactive routing and forwarding all working cohesively to provide the first complete systems solution. We describe the development of a real-life ad hoc network testbed using UDAAN with switched Directional Antennas, and we discuss the lessons learned during field trials. High fidelity simulation results, using the same networking code as in the prototype, are also presented. For the range of parameters studied, our results show that UDAAN can produce up to a factor-of-10 improvement in throughput over omni-Directional communications.
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using Directional Antennas for medium access control in ad hoc networks
ACM IEEE International Conference on Mobile Computing and Networking, 2002Co-Authors: Romit Roy Choudhury, Ram Ramanathan, Xue Yang, Nitin H. VaidyaAbstract:Previous research in wireless ad hoc networks typically assumes the use of omniDirectional Antennas at all nodes. With omniDirectional Antennas, while two nodes are communicating using a given channel, MAC protocols such as IEEE 802.11 require all other nodes in the vicinity to stay silent. With Directional Antennas, two pairs of nodes located in each other's vicinity may potentially communicate simultaneously, depending on the directions of transmission. This can increase spatial reuse of the wireless channel. In addition, the higher gain of Directional Antennas allows a node to communicate with other nodes located far away, implying that messages could be delivered to the destination in fewer hops. In this paper, we propose a MAC protocol that exploits the characteristics of Directional Antennas. Our design focuses on using multi-hop RTSs to establish links between distant nodes, and then transmit CTS, DATA and ACK over a single hop. Results show that our Directional MAC protocol can perform better than IEEE 802.11, although we find that the performance is dependent on the topology configuration and the flow patterns in the system.