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Medium access control for 60 GHz outdoor mesh networks with highly directional links
"... Abstract — We investigate an architecture for multiGigabit outdoor mesh networks operating in the unlicensed 60 GHz “millimeter (mm) wave ” band. In this band, the use of narrow beams is essential for attaining the required link ranges in order to overcome the higher path loss at mm wave carrier fr ..."
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Abstract — We investigate an architecture for multiGigabit outdoor mesh networks operating in the unlicensed 60 GHz “millimeter (mm) wave ” band. In this band, the use of narrow beams is essential for attaining the required link ranges in order to overcome the higher path loss at mm wave carrier frequencies. However, highly directional links make standard MAC methods for interference management, such as carrier sense multiple access, which rely on neighboring nodes hearing each other, become inapplicable. In this paper, we study the extent to which we can reduce, or even dispense with, interference management, by exploiting the reduction in interference due to the narrow beamwidths and the oxygen absorption characteristic of the 60 GHz band. We provide a probabilistic analysis of the interference incurred due to uncoordinated transmissions, and show that, for the parameters considered, the links in the network can be thought of as pseudowired. That is, interference can essentially be ignored in MAC design, and the challenge is to schedule halfduplex transmissions in the face of the “deafness” resulting from highly directional links. We provide preliminary simulation results to validate our approach. I.
Asymptotic Connectivity in Wireless Ad Hoc Networks Using Directional Antenna
 IEEE/ ACM Trans. Networking
, 2009
"... Abstract—Connectivity is a crucial issue in wireless ad hoc networks (WANETs). Gupta and Kumar have shown that in WANETs using omnidirectional antennas, the critical transmission range to achieve asymptotic connectivity is if nodes are uniformly and independently distributed in a disk of unit ..."
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Abstract—Connectivity is a crucial issue in wireless ad hoc networks (WANETs). Gupta and Kumar have shown that in WANETs using omnidirectional antennas, the critical transmission range to achieve asymptotic connectivity is if nodes are uniformly and independently distributed in a disk of unit area. In this paper, we investigate the connectivity problem when directional antennas are used. We first assume that each node in the network randomly beamforms in one beam direction. We find that there also exists a critical transmission range for a WANET to achieve asymptotic connectivity, which corresponds to a critical transmission power (CTP). Since CTP is dependent on the directional antenna pattern, the number of beams, and the propagation environment, we then formulate a nonlinear programming problem to minimize the CTP. We show that when directional antennas use the optimal antenna pattern, the CTP in a WANET using directional antennas at both transmitter and receiver is smaller than that when either transmitter or receiver uses directional antenna and is further smaller than that when only omnidirectional antennas are used. Moreover, we revisit the connectivity problem assuming that two neighboring nodes using directional antennas can be guaranteed to beamform to each other to carry out the transmission. A smaller critical transmission range than that in the previous case is found, which implies smaller CTP. Index Terms—Wireless ad hoc networks, directional antenna, asymptotic connectivity, critical transmission range, critical transmission power. I.
Impact of Radio Link Unreliability on the Connectivity of Wireless Sensor Networks
, 2007
"... Many works have been devoted to connectivity of ad hoc networks. This is an important feature for wireless sensor networks (WSNs) to provide the nodes with the capability of communicating with one or several sinks. In most of these works, radio links are assumed ideal, that is, with no transmission ..."
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Cited by 10 (3 self)
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Many works have been devoted to connectivity of ad hoc networks. This is an important feature for wireless sensor networks (WSNs) to provide the nodes with the capability of communicating with one or several sinks. In most of these works, radio links are assumed ideal, that is, with no transmission errors. To fulfil this assumption, the reception threshold should be high enough to guarantee that radio links have a low transmission error probability. As a consequence, all unreliable links are dismissed. This approach is suboptimal concerning energy consumption because unreliable links should permit to reduce either the transmission power or the number of active nodes. The aim of this paper is to quantify the contribution of unreliable long hops to an increase of the connectivity of WSNs. In our model, each node is assumed to be connected to each other node in a probabilistic manner. Such a network is modeled as a complete random graph, that is, all edges exist. The instantaneous node degree is then defined as the number of simultaneous valid singlehop receptions of the same message, and finally the mean node degree is computed analytically in both AWGN and blockfading channels. We show the impact on connectivity of two MACs and routing parameters. The first one is the energy detection level such as the one used in carrier sense mechanisms. The second one is the reliability threshold used by the routing layer to select stable links only. Both analytic and simulation results show that using opportunistic protocols is challenging.
Analytical study of connectivity in wireless ad hoc networks with random beamforming
 In Proc. Int. Conf. on Signal Processing and Communication Systems (ICSPCS), Gold
, 2007
"... Abstract — Random beamforming is a technique in which each node in a wireless ad hoc network directs its main beam in a randomly chosen direction. This paper presents an analytical method for investigating the effect of random beamforming on the connectivity of wireless ad hoc networks. We derive an ..."
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Abstract — Random beamforming is a technique in which each node in a wireless ad hoc network directs its main beam in a randomly chosen direction. This paper presents an analytical method for investigating the effect of random beamforming on the connectivity of wireless ad hoc networks. We derive analytically an expression for an effective beamforming gain, which we use to characterize the impact of random beamforming on the number of direct connections for an arbitrary node, i.e. the local connectivity. Our results show that for a pathloss propagation model, random beamforming improves the local connectivity for a pathloss exponent α < 3, while it degrades the local connectivity for larger values of α. The analytical method is validated by comparison with simulation results. I.
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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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.
Interference Modeling in CSMA MultiHop Wireless Networks
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Asymptotic connectivity in wireless networks using directional antennas
 International Conference on Distributed Computing Systems 2007 article No. 4268197
"... Connectivity is a crucial issue in wireless networks. Gupta and Kumar show that with omnidirectional antennas, the critical transmission range for a wireless network to achieve asymptotic connectivity is O( logn n) if n nodes are uniformly and independently distributed in a disk of unit area. In th ..."
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Connectivity is a crucial issue in wireless networks. Gupta and Kumar show that with omnidirectional antennas, the critical transmission range for a wireless network to achieve asymptotic connectivity is O( logn n) if n nodes are uniformly and independently distributed in a disk of unit area. In this paper, we investigate the connectivity problem when directional antennas are used. We find that there also exists a critical transmission range, which corresponds to a critical transmission power. We show that in the same propagation environment, when directional antennas use the optimal antenna pattern, the critical transmission power could be much smaller than that in networks using omnidirectional antennas. Moreover, to achieve asymptotic connectivity, it is known that each node has to have O(log n) neighbors when using omnidirectional antennas. We show that even using the transmission power level at which each node has only O(1) neighbors when using omnidirectional antennas, we can still achieve the asymptotic connectivity with directional antennas. 1.
Eavesdropping Security in Wireless Ad Hoc Networks with Directional Antennas
"... Abstract—The eavesdropping security of wireless ad hoc networks has attracted considerable attention recently. However, most of current studies only consider OMN networks, where each node is mounted with a single omnidirectional antenna, which radiates radio signals in all directions and consequen ..."
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Abstract—The eavesdropping security of wireless ad hoc networks has attracted considerable attention recently. However, most of current studies only consider OMN networks, where each node is mounted with a single omnidirectional antenna, which radiates radio signals in all directions and consequently leads to the high eavesdropping possibility. Compared with an omnidirectional antenna, a directional antenna can concentrate the radio signals on some desired directions so that it can potentially reduce the eavesdropping possibility. This paper investigates the eavesdropping security of wireless ad hoc networks equipped with directional antennas. In particular, we study the eavesdropping possibility of OMN networks, SDA networks in which each node is equipped with a simplistic directional antenna and RDA networks in which each node is equipped with a realistic directional antenna. More specifically, we identify the eavesdropping activity in wireless networks and propose an eavesdropping model to measure the eavesdropping possibility. We conduct extensive simulations to evaluate the eavesdropping possibility of OMN networks, SDA networks and RDA networks with considering various environment factors, such as path loss attenuation and shadowing effects. Our simulation results show that using a simplistic directional antenna or a realistic antenna in wireless networks can reduce the eavesdropping possibility. I.
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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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.
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.