• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권11호
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• pp.5218-5233
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• 2018

The coexisting wireless body area networks (WBAN) is a very challenging issue because of strong inter-networks interference, which seriously affects energy consumption and spectrum utilization ratio. In this paper, we study a power control strategy with nearest neighbor nodes distribution for coexisting WBAN based on stochastic geometry. Using homogeneous Poisson point processes (PPP) model, the relationship between the transmission power and the networks distribution is analytically derived to reduce interference to other devices. The goal of this paper is to increase the transmission success probability and throughput through power control strategy. In addition, we evaluate the area spectral efficiency simultaneously active WBAN in the same channel. Finally, extensive simulations are conducted to evaluate the power control algorithm.

• ETRI Journal
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• 제34권3호
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• pp.297-307
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• 2012

A femtocell is a small cellular base station, typically designed for use in a home or small business. The random deployment of a femtocell has a critical effect on the performance of a macrocell network due to co-channel interference. Utilizing the advantage of a multiple-input multiple-output system, each femto base station (FBS) is able to form a cluster and generates a precoding matrix, which is a modified version of conventional single-cell block diagonalization, in a cooperative manner. Since interference from clustered-FBSs located at the nearby macro user equipment (MUE) is the dominant interference contributor to the coexisting networks, each cluster generates a precoding matrix considering the effects of interference on nearby MUEs. Through simulation, we verify that the proposed algorithm shows better performance respective to both MUE and femto user equipment, in terms of capacity.

• Journal of Communications and Networks
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• 제18권3호
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• pp.340-350
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• 2016

The performance of large-scale cognitive radio (CR) networks with secondary users sustained by opportunistically harvesting radio-frequency (RF) energy from nearby primary transmissions is investigated. Using an advanced RF energy harvester, a secondary user is assumed to be able to collect ambient primary RF energy as long as it lies inside the harvesting zone of an active primary transmitter (PT). A variable power (VP) transmission mode is proposed, and an energy-based opportunistic spectrum access (OSA) strategy is considered, under which a secondary transmitter (ST) is allowed to transmit only if its harvested energy is larger than a predefined transmission threshold and it is outside the guard zones of all active PTs. The transmission probability of the STs is derived. The outage probabilities and the throughputs of the primary and the secondary networks, respectively, are characterized. Compared with prior work, the throughput can be increased by as much as 29%. The energy-based OSA strategy can be generally applied to a non-CR setup, where distributed power beacons (PBs) are deployed to power coexisting wireless signal transmitters (WSTs) in a wireless powered sensor network.

• International Journal of Computer Science & Network Security
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• 제23권12호
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• pp.194-198
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• 2023

The current electricity networks will undergo profound changes in the years to come to be able to meet the growing demand for electricity, while minimizing the costs of consumers and producers, etc. The electricity network of tomorrow or even the intelligent « Smart Grids » network will be the convergence of two networks: the electricity network and the telecommunications network. In this context falls our work which aims to study the impact of the integration of energy decentralization into the electricity network. In this sense, we have implemented a new smart grid model where several coexisting suppliers can exchange information with consumers in real time. In addition, a new approach to energy distribution optimization has been developed. The simulation results prove the effectiveness of this approach in improving energy exchange and minimizing consumer purchase costs and line losses.

• International Journal of Internet, Broadcasting and Communication
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• 제12권4호
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• pp.226-231
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• 2020

In order to maximize the production of landscape plants in optimal condition while coexisting with the environment in terms of precision agriculture, quick and accurate information gathering of the internal environmental elements of the growing container is necessary. This may depend on the accuracy of the positioning of numerous sensors connected to landscape plants cultivating system (LPCS) in containers. Thus, this paper presents a method for estimating the location of the sensors related to cultivation environment connected to LPCS by measuring the received signal strength (RSS) or time of arrival TOA received between oneself and adjacent sensors. The Small sensors connected to the LPCS of container are known for their locations, but the remaining locations must be estimated. For this in the paper, Rao-Cramer limits and maximum likelihood estimators are derived from Gaussian models and lognormal models for TOA and RSS measurements, respectively. As a result, this study suggests that both RSS and TOA range measurements can produce estimates of the exact locations of the cultivation environment sensors within the wireless sensor network related to the LPCS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권5호
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• pp.980-997
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• 2013

Nowadays, wireless communication has a great advantage in technology. We use wireless devices almost in all expected life such as: entertainment, working and recently in the healthcare area, where Wireless Body Area Networks (WBANs) become a hot topic for researchers and system designers. Recent work on WBANs focus on related issues to communication protocol, especially ZigBee network is fine tuned to meet particular requirements in healthcare area. For example, some papers present real-time patient monitoring via ZigBee communication given the short distance between body sensors and remote devices, while the other work solve the limited coverage problem of Zigbee by designing mechanisms to relay Zigbee data to other types of wire or wireless infrastructure. However, very few of them investigate the scenarios of ZigBee coexisting or integrated with other networks. In this paper, we present the real-time data transmission from ZigBee end devices to Wide Area Network (WAN), Worldwide interoperation for microwave access network (WiMAX) and Long Term Evolution network (LTE). We provide in detail the ZigBee gateway components. Our simulation is conducted by OPNET, we visualize many topology network scenarios in ZigBee hybrid system. The results in simulation show that ZigBee end devices can successfully transmit data in real-time to other network end devices.

• 한국정보과학회논문지:정보통신
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• 제35권1호
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• pp.11-20
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• 2008

차세대 무선 네트워크 환경의 필연적인 추세는 상이한 특성을 가지는 무선 액세스 네트워크들이 상호 보완적인 방법으로 공존한다는 것이다. 또한 두 개 이상의 에어 인터페이스를 갖추고 다양한 서비스를 동시에 받을 수 있는 이동 단말들도 등장하고 있다. 이와 같은 환경에서 이동 사용자가 이질의 액세스 네트워크 간을 로밍하는 경우에도 끊김없는 통신을 지속할 수 있도록 해 주고, 여러 개의 공존하는 무선 액세스 네트워크들을 효과적으로 활용함으로써 응용 별 서비스품질 요구를 만족할 수 있는 해결책이 필요하다. 이에 본 연구에서는 응용 별 종단 간 이동성 관리와 cross-layer 핸드오버 제어에 기반한 이동성 관리 플랫폼을 제안한다. 제안하는 플랫폼은 종단 사용자의 단말에서 동작하며, Monitoring Agent, Profile Database, Decision Engine, IP Agent 등 4개의 기능적인 모듈로 구성된다. 시뮬레이션을 통해 제안하는 플랫폼이 응용 별로 적합한 액세스 네트워크를 선택함으로써 향상된 QoS를 제공함을 보였다.

• Journal of Communications and Networks
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• 제10권1호
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• pp.63-70
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• 2008

Narrow-band interference (NBI) from the coexisting narrow-band services affects the performance of ultra wideband (UWB) systems considerably due to the high power of these narrow-band signals with respect to the UWB signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals may interfere with UWB systems significantly. In this paper, we suggest a novel NBI suppression technique based on singular value decomposition (SVD) algorithm in time hopping UWB (TH-UWB) systems. SVD is used to approximate the interference which then is subtracted from the received signals. The algorithm precision and closed-form bit error rate (BER) expression are derived in the wireless multipath channel. Comparing with the conventional suppression methods such as a notch filter and a RAKE receiver, the proposed method is simple and robust and especially suitable for UWB systems.

• Journal of Communications and Networks
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• 제16권2호
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• pp.227-237
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• 2014

Throughput scaling laws for two coexisting ad hoc networks with m primary users (PUs) and n secondary users (SUs) randomly distributed in an unit area have been widely studied. Early work showed that the secondary network performs as well as stand-alone networks, namely, the per-node throughput of the secondary networks is ${\Theta}(1/\sqrt{n{\log}n})$. In this paper, we show that by exploiting directional spectrum opportunities in secondary network, the throughput of secondary network can be improved. If the beamwidth of secondary transmitter (TX)'s main lobe is ${\delta}=o(1/{\log}n)$, SUs can achieve a per-node throughput of ${\Theta}(1/\sqrt{n{\log}n})$ for directional transmission and omni reception (DTOR), which is ${\Theta}({\log}n)$ times higher than the throughput with-out directional transmission. On the contrary, if ${\delta}={\omega}(1/{\log}n)$, the throughput gain of SUs is $2{\pi}/{\delta}$ for DTOR compared with the throughput without directional antennas. Similarly, we have derived the throughput for other cases of directional transmission. The connectivity is another critical metric to evaluate the performance of random ad hoc networks. The relation between the number of SUs n and the number of PUs m is assumed to be $n=m^{\beta}$. We show that with the HDP-VDP routing scheme, which is widely employed in the analysis of throughput scaling laws of ad hoc networks, the connectivity of a single SU can be guaranteed when ${\beta}$ > 1, and the connectivity of a single secondary path can be guaranteed when ${\beta}$ > 2. While circumventing routing can improve the connectivity of cognitive radio ad hoc network, we verify that the connectivity of a single SU as well as a single secondary path can be guaranteed when ${\beta}$ > 1. Thus, to achieve the connectivity of secondary networks, the density of SUs should be (asymptotically) bigger than that of PUs.

• 한국통신학회논문지
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• 제36권10B호
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• pp.1182-1191
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• 2011

본 논문에서는 망 기반의 IP 이동성 지원 기술인 AIMS 기술을 기반으로 IPv4와 IPv6가 혼재된 망 환경에서 이동 단말에 대한 끊김 없는 이동성을 지원하는 AIMS-DS 기술을 제안하였다. 제안된 AIMS-DS 기술은 IPv4와 IPv6 프로토콜을 모두 지원하는 듀얼스택 단말에 대하여 IPv4와 IPv6 홈 주소들에 대한 이동성 지원 방안을 제안함으로써, IPv4와 IPv6가 혼재되어 공존하는 과도기적인 망 환경에서 양단간 끊김 없는 이동성 서비스를 제공할 수 있다. 본 논문에서는 액세스 망과 코어 망의 IP 버전에 따른 4가지 경우에 대하여 양단간 패킷 전달 지연 시간과 핸드오버 지연시간에 대하여 AIMS-DS에 대한 성능 분석을 수행하였다.