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17
The Capacity of Heterogeneous Wireless Networks
 Proc. IEEE INFOCOM
, 2010
"... Abstract—A substantial body of the literature exists addressing the capacity of wireless networks. However, it is commonly assumed that all nodes in the network are identical. The issue of heterogeneity has not been embraced into the discussions. In this paper, we investigate the throughput capacity ..."
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Cited by 14 (3 self)
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Abstract—A substantial body of the literature exists addressing the capacity of wireless networks. However, it is commonly assumed that all nodes in the network are identical. The issue of heterogeneity has not been embraced into the discussions. In this paper, we investigate the throughput capacity of heterogeneous wireless networks with general network settings. Specifically, we consider an extended network with n normal nodes and m nb (0 b 1) more powerful helping nodes in a rectangular area with width sðnÞ and length n=sðnÞ, where sðnÞ nw and 0 w 1=2. We assume that there are n flows in the network. All the n normal nodes are sources while only randomly chosen nd (0 d 1) normal nodes are destinations. We further assume that the n normal nodes are uniformly and independently distributed, while the m helping nodes are either regularly placed or uniformly and independently distributed, resulting in two different kinds of networks called Regular Heterogeneous Wireless Networks and Random Heterogeneous Wireless Networks, respectively. We show that network capacity is determined by the shape of the network area, the number of destination nodes, the number of helping nodes, and the bandwidth of helping nodes. We also find that heterogeneous wireless networks can provide throughput higher in the order sense than traditional homogeneous wireless networks only under certain conditions. Index Terms—Heterogeneous wireless networks, extended networks, achievable throughput Ç 1
On the connectivity of wireless networks with multiple directional antennas
 in Networks (ICON), 2012 18th IEEE International Conference on. IEEE, 2012
"... Abstract—The network connectivity is one of important measures of the performance of wireless networks. However, most of current studies on the network connectivity only consider either an SOMN network, where each node is mounted with a single omnidirectional antenna, or an SDA network, where each ..."
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Cited by 4 (2 self)
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Abstract—The network connectivity is one of important measures of the performance of wireless networks. However, most of current studies on the network connectivity only consider either an SOMN network, where each node is mounted with a single omnidirectional antenna, or an SDA network, where each node is mounted with a single directional antenna. Using multiple directional antennas instead of a single directional antenna can potentially improve the network performance. In this paper, we investigate the connectivity of a novel network, in terms of an MDA network, where each node is mounted with multiple directional antennas. We found that MDA networks have much stronger network connectivity than other existing networks (such as SOMN and SDA networks), and its connectivity degree heavily depends on the number of antennas, the beamwidth of each antenna and the path loss factor. The enhancement mainly owes to the usage of multiple antennas and the longer transmission range of directional antennas.
Analysis of capacity improvement by directional antennas in wireless sensor networks
 ACM Trans. Sensor Netw. 2012
"... In this paper we analyze the capacity improvement by directional antennas over omniantennas in wireless sensor networks. The capacity in our analysis is the endtoend pernode throughput. We analyze the typical traffic pattern for sensor networks, where traffics are destined to or originated from ..."
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Cited by 2 (0 self)
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In this paper we analyze the capacity improvement by directional antennas over omniantennas in wireless sensor networks. The capacity in our analysis is the endtoend pernode throughput. We analyze the typical traffic pattern for sensor networks, where traffics are destined to or originated from the sink. The main results of our analysis are summarized as follows: 1) The network capacity is O(1/N) for both omni and directional antennas, where N is number of sensor nodes in the network. 2) In the case of line deployment, the capacity ratio of directional antennas over omni antennas is bounded by (2q+3)/(2q−1), where q is the ratio of interference radius to transmission radius. 3) In the case of twodimensional deployment, the capacity of using directional antennas is O ( 1 θ) for m = 2, and O ( lgm θ2 lg(1/θ)) for m> 2, where m is the number of radios (antennas) on each node, and θ is the beamwidth of antennas. 4) When there are n> 1 sinks, the capacity has a nonmonotonic relationship with the transmission radius. The optimal transmission radius depends on the ratio of n/q. 5) The capacity ratio of directional antennas over omni antennas in multichannels networks decreases as the increase of channel number/radio number ratio c/m.
Floating information with stationary nodes
"... Abstract—In the Floating Content application, mobile nodes collectively store and disseminate messages relevant to a certain area by using the principles of opportunistic networking. The system operates in best effort fashion relying solely on the nodes located in the area of interest, which is refe ..."
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Abstract—In the Floating Content application, mobile nodes collectively store and disseminate messages relevant to a certain area by using the principles of opportunistic networking. The system operates in best effort fashion relying solely on the nodes located in the area of interest, which is referred to as the anchor zone of the message. Past work has focused on mobility models, where the nodes are constantly moving and the messages are exchanged “onthefly”. In this paper, we consider the case, where messages can be exchanged only when two nodes are stationary within each others ’ transmission range. Our objective is to characterize when the information floats, that is, when it is likely to remain available for long periods of time. We find that there exists a certain threshold for the mean node degree, which we refer to as the permanence threshold, above which the expected lifetime of the information increases very rapidly (in a finite system) or the information becomes permanent (in an infinite system). This threshold is about 1.3 for the basic case (a single stop per visit), which is clearly below the percolation threshold of about 4.5. Additional stops within the zone improve the situation further. I.
1Connectivity of confined 3D Networks with Anisotropically Radiating Nodes
"... Abstract—Nodes in ad hoc networks with randomly oriented directional antenna patterns typically have fewer short links and more long links which can bridge together otherwise isolated subnetworks. This network feature is known to improve overall connectivity in 2D random networks operating at low ch ..."
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Abstract—Nodes in ad hoc networks with randomly oriented directional antenna patterns typically have fewer short links and more long links which can bridge together otherwise isolated subnetworks. This network feature is known to improve overall connectivity in 2D random networks operating at low channel path loss. To this end, we advance recently established theoretical results to obtain analytic expressions for the mean degree of 3D networks for simple but practical anisotropic gain profiles, including those of patch, dipole and endfire array antennas. Our analysis reveals that for homogeneous systems (i.e. neglecting boundary effects) directional radiation patterns are superior to the isotropic case only when the path loss exponent is less than the spatial dimension. Moreover, we establish that ad hoc networks utilizing directional transmit and isotropic receive antennas (or vice versa) are always suboptimally connected regardless of the environment path loss. We extend our analysis to investigate inhomogeneous systems, and study the geometrical reasons why boundary effects cause directional radiating nodes to be at a disadvantage to isotropic ones. Finally, we discuss multidirectional gain patterns consisting of many equally spaced lobes which could be used to mitigate boundary effects and improve overall network connectivity. I.
Doctoral Thesis Exact Throughput Capacity Studies for Mobile Ad Hoc Networks by
, 2014
"... The rapid development of wireless communication technology has made mobile ad hoc networks (MANETs) an increasingly appealing option for a lot of critical applications, such as daily information exchange, disaster relief, vehicular networks and military communication. A major obstacle, however, stun ..."
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The rapid development of wireless communication technology has made mobile ad hoc networks (MANETs) an increasingly appealing option for a lot of critical applications, such as daily information exchange, disaster relief, vehicular networks and military communication. A major obstacle, however, stunting the application of MANETs is the lack of understanding on the throughput capacity, i.e., the maximum achievable throughput between node pairs, of these networks. By now, a great deal of research activity has been conducted for throughput capacity in MANETs, most of which focused on exploring the scaling behaviors of the throughput capacity as the network size increases. Despite the insights provided by the scaling law results, they tell us little about the actual achievable throughput of a MANET, which is of great interest for network designers. Although there are some preliminary efforts towards the exact studies, the exact throughput capacity remains unknown for many important MANET scenarios. In this thesis, we study the exact throughput capacity for three important network
8th International Workshop on Spatial Stochastic Models for Wireless Networks, 14 May 2012 Floating information with stationary nodes
"... Abstract—In the Floating Content application, mobile nodes collectively store and disseminate messages relevant to a certain area by using the principles of opportunistic networking. The system operates in best effort fashion relying solely on the nodes located in the area of interest, which is refe ..."
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Abstract—In the Floating Content application, mobile nodes collectively store and disseminate messages relevant to a certain area by using the principles of opportunistic networking. The system operates in best effort fashion relying solely on the nodes located in the area of interest, which is referred to as the anchor zone of the message. Past work has focused on mobility models, where the nodes are constantly moving and the messages are exchanged “onthefly”. In this paper, we consider the case, where messages can be exchanged only when two nodes are stationary within each others ’ transmission range. Our objective is to characterize when the information floats, that is, when it is likely to remain available for long periods of time. We find that there exists a certain threshold for the mean node degree, which we refer to as the permanence threshold, above which the expected lifetime of the information increases very rapidly (in a finite system) or the information becomes permanent (in an infinite system). This threshold is about 1.3 for the basic case (a single stop per visit), which is clearly below the percolation threshold of about 4.5. Additional stops within the zone improve the situation further. I.
Impact of Nakagamim Fading Model on Multihop
"... Several theoretical and experimental based models have been proposed to predict the fading envelope of the received signal in multipath condition. In this paper, we considered a model named Nakagamim model. Nakagamim can model a variety of fading environments, where it closely approximates the Nak ..."
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Several theoretical and experimental based models have been proposed to predict the fading envelope of the received signal in multipath condition. In this paper, we considered a model named Nakagamim model. Nakagamim can model a variety of fading environments, where it closely approximates the Nakagamiq (Hoyt) and the Nakagamin (Rice) models, and has the Rayleigh and one sided Gaussian models as special cases. This model provides the best fit to landmobile system like wireless mobile ad hoc Network (MANET). Under Nakagamim fading model, received packet may not be clearly understood by the receiving node, which affects the routing protocol as well as the medium access control protocol of a network. The severity of Nakagamim fading model on the network performance has been presented in this paper which is demonstrated via simulation results. Simulation results illustrate that the performance of a network may become unable to meet the expectation if Nakagamim fading model is used in contrast to the simple tworay model. A physical layer solution and a Medium Access Control (MAC) layer solution been proposed in this paper to overcome the effects of Nakagamim fading model. Simulation results prove that these two solutions condense the Nakagamim fading effect and improve network performance.
unknown title
"... This paper investigates the issue of connectivity of a wireless adhoc network in the presence of channel impairments. We derive analytical expressions for the node isolation probability in an adhoc network in the presence of Nakagamim fading with superimposed lognormal shadowing. The node isolation ..."
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This paper investigates the issue of connectivity of a wireless adhoc network in the presence of channel impairments. We derive analytical expressions for the node isolation probability in an adhoc network in the presence of Nakagamim fading with superimposed lognormal shadowing. The node isolation probability is the probability that a randomly chosen node is not able to communicate with none of the other nodes in the network. An extensive investigation into the impact of path loss exponent, lognormal shadowing, Nakagami fading severity index, node density, and diversity order on the node isolation probability is conducted. The presented results are beneficial for the practical design of ad hoc networks.