• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1B
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• pp.9-14
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• 2012

The neighbor discovery using directional antennas in mmWave band is a prerequisite for communications and this issue is crucial and urgent. In this paper, the synchronized, direct, two-way directional neighbor discovery process is analyzed mathematically for mmWave WPANs. The analysis is based on the values which are derived from the effect of using directional antennas. The neighbor discovery probability for a given amount of time is considered and several performance measures such as the optimal sojourn time are derived in closed forms. Numerical results are obtained using parameters based on the IEEE 802.15.3c. The mathematical analysis provides the theoretical basis for the directional neighbor discovery process.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.14-19
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• 2017

In this paper, a planar directional beam-switchable antenna with four orthogonal beam directions is proposed. The proposed antenna is designed with two crossed active elements and two parasitic elements for each direction. The design methodology is described on the basis of the Yagi-Uda method for the active and parasitic elements, respectively. By adjusting the effective electric lengths of the parasitic elements, the roles of a director and a reflector are exchanged with each other. The planar four-way beam-switchable Yagi-Uda antenna is implemented. From the experimental results. The proposed design method is verified for orthogonal radiation beam switching.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.232-238
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• 2004

In this paper, radio propagation in a subway tunnel is investigated using fan beam antennas, circular polarization antennas and directional antennas at 2.4㎓ and 5.8㎓ band, respectively. The results of narrowband channel measurements show that received power level for NLOS(Non-Line-Of-Sight) path is decreased drastically as compared with LOS(Line-Of-Sight) path. Wideband channel measurements are obtained using a PN sliding correlation method. The parameters of the channel such as mean access delay and RMS delay spread are compared as to different types of directional beam at IEEE 802.11 WLAN(Wireless Local Area Network) band including 2.4㎓ and 5.8㎓ bands, respectively.

• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.20-30
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• 2019

A wide-band multiple-input multiple-output (MIMO) antenna with dual-band (2.4 and 5 GHz) operation is proposed for premium indoor access points (IAPs). Typically, an omni-directional pattern is used for dipole antennas and a directional radiation pattern is used for patch antennas. In this paper, both antenna types were used to compare their performance with that of the proposed $2{\times}2$ MIMO antenna. We simulated and measured the performance of the MIMO antenna, including the isolation, envelope correlation coefficient (ECC), mean effective gain (MEG) for the IAPs, and the throughput, in order to determine its communication quality. The performance of the antennas was analyzed according to the ECC and MEG. The proposed antenna has sufficient performance and excellent characteristics, making it suitable for IAPs. We analyzed the communication performance of wireless networks using the throughput data of a typical office environment. The network throughput of an 802.11n device was used for the comparison and was conducted according to the antenna type. The results showed that the values of the ECC, MEG, and the throughput have unique characteristics in terms of their directivity, antenna gains, isolation, etc. This paper also discusses the communication performance of various aspects of MIMO in multipath situations.

• ETRI Journal
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• v.42 no.3
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• pp.351-365
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• 2020

Directional sensor networks (DSNs) can significantly improve the performance of a network by employing energy efficient communication protocols. Neighbor discovery is a vital part of medium access control (MAC) and routing protocol, which influences the establishment of communication between neighboring nodes. Neighbor discovery is a challenging task in DSNs due to the limited coverage provided by directional antennas. Furthermore, in these networks, communication can only take place when the beams of the directional antennas are pointed toward each other. In this article, we propose a novel multiple token-based neighbor discovery (MuND) protocol, in which multiple tokens are transmitted based on an area exploration algorithm. The performance of the protocol is evaluated using the Cooja simulator. The simulation results reveal that the proposed MuND protocol achieves lower neighbor discovery latency, with a 100% neighbor discovery ratio, and has a relatively low communication overhead and low energy consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.278-286
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• 2011

Directional antennas have been used in Ad Hoc networks, significantly improving the spatial reuse of the networks. However, the extended transmission range causes collisions at the receivers of neighbors, which prevents full exploitation of the potential of the directional antenna. In this paper, we propose a new power control MAC protocol for a directional antenna. For this protocol, we propose a method to detect a set of interference nodes in the neighbors of a receiver. We then use a power control algorithm to calculate the minimum transmission power and send data. Simulation results demonstrate that this protocol increases the network performance and reduces energy consumption.

• ETRI Journal
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• v.36 no.3
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• pp.374-384
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• 2014

To achieve high-speed (giga-bit) connectivity for short-range wireless multimedia applications, the millimeter-wave (mmWave) wireless personal area networks with directional antennas are gaining increased interest. Due to the use of directional antennas and mmWave communications, the probability of non-interfering transmissions increases in a localized region. Network throughput can be increased immensely by the concurrent time allocation of non-interfering transmissions. The problem of finding optimum time allocation for concurrent transmissions is an NP-hard problem. In this paper, we propose two enhanced versions of previously proposed multi-hop concurrent transmission (MHCT) schemes. To increase network capacity, the proposed schemes efficiently make use of the free holes in the time-allocation map of the MHCT scheme; thus, making it more compact.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2447-2458
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• 2009

Ad hoc wireless networks operate without any infrastructure where a node can be a source and a router at the same time. This indispensably requires high throughput and low delay performance throughout the wireless network coverage span, particularly under heavy traffic conditions. Recent research on using multiple antennas in beam-forming or multiplexing modes over a wireless channel has shown promising results in terms of high throughput and low delay. Directional antennas have shown to increase spatial reuse by allowing multiple transmitters and receivers to communicate using. directional beams as long as they do not significantly interfere with each other. However directional antenna performance asymptotically approaches the omni-directional performance in a high density ad hoc network. Simulation results in QualNet validate that average throughput and packet corruption ratio of directional antenna approach omni-directional performance. Moreover, we further highlight some important issues pertaining to the directional antenna performance in wireless networks.

• ETRI Journal
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• v.36 no.3
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• pp.385-395
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• 2014

In this paper, we consider a resource allocation scheme for millimeter wave-based wireless personal area networks using directional antennas. This scheme involves scheduling the reservation period of medium access control for IEEE 802.15.3c. Objective functions are considered to minimize the average delay and maximize throughput; and two scheduling algorithms-namely, MInMax concurrent transmission and MAxMin concurrent transmission-are proposed to provide a suboptimal solution to each objective function. These are based on an exclusive region and two decision rules that determine the length of reservation times and the transmission order of groups. Each group consists of flows that are concurrently transmittable via spatial reuse. The algorithms appropriately apply two decision rules according to their objectives. A real video trace is used for the numerical results, which show that the proposed algorithms satisfy their objectives. They outperform other schemes on a range of measures, showing the effect of using a directional antenna. The proposed scheme efficiently supports variable bit rate traffic during the reservation period, reducing resource waste.

• Journal of Korea Multimedia Society
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• v.10 no.1
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• pp.94-101
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• 2007

Partial dominant pruning(PDP) is regarded as the most practical scheme, reducing redundant messages arisen in broadcasting over ad hoc networks, in such a way that only part of nodes are allowed to forward the received broadcast message. In this paper we propose an extend PDP version called DPDP(directional PDP) such that it reduces not only the number of selected forward nodes, but also the number of antenna elements deployed by the forward nodes. It turns out through simulation that as the number of antenna elements increases, the number of selected forward nodes by DPDP slightly outnumbers that obtained using PDP but both the number of antenna elements deployed by the forward nodes and the redundancy ratio of the received message per node always outperform respectively those given by PDP.