• Journal of Digital Contents Society
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• v.7 no.2
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• pp.103-108
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• 2006

Short-range wireless communication and networking technologies are becoming increasingly important in enabling useful mobile applications. for example, ZigBee technology is expected to provide low cost and low power connectivity for equipment that needs battery life as long as several months to several years. In addition, ZigBee can be implemented in mesh networks larger than is possible with Bluetooth. The main features of this ZigBee standard are network flexibility, low cost, very low power consumption, and low data rate in an adhoc self-organizing network among fixed, portable and moving devices. Home network/Home automation is one of the key market areas for Zigbee, with an example of a simple network This paper investigates the effect of short range wireless channel on the performance of Zigbee system and DSSS-BPSK signal transmission in AWGN, interference and Rician fading environments. And we investigate performance degradation due to interference and fading effects in short range wireless channel. In particular, the impacts of the fading and interference level on the bit error probability is shown in BER performance figures.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.65-70
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• 2013

In this paper, we propose a multi-hop cooperative transmission protocol to obtain energy savings in static wireless networks. Each terminal in the network is equipped with a single antenna and each receiver uses equal gain combining technique (EGC) to combine received signals. We also propose a power allocation strategy which optimizes the total transmit power at each stage. Monte-Carlo simulations are presented to evaluate and compare performance of the proposed protocol with the multi-hop direct transmission (MDT) and the cooperative routing protocol proposed by Khadani [8], in terms of the average total transmit power and the average number of required stages.

• Journal of information and communication convergence engineering
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• v.22 no.1
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• pp.1-6
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• 2024

Energy efficiency in wireless sensor networks (WSNs) is a critical issue because batteries are used for operation and communication. In terms of scalability, energy efficiency, data integration, and resilience, WSN-cluster-based routing algorithms often outperform routing algorithms without clustering. Low-energy adaptive clustering hierarchy (LEACH) is a cluster-based routing protocol with a high transmission efficiency to the base station. In this paper, we propose an energy consumption model for LEACH and compare it with the existing LEACH, advanced LEACH (ALEACH), and power-efficient gathering in sensor information systems (PEGASIS) algorithms in terms of network lifetime. The energy consumption model comprises energy-sensitive cluster formation and a cluster head selection technique. The setup and steady-state phases of the proposed model are discussed based on the cluster head selection. The simulation results demonstrated that a low-energy-consumption network was introduced, modeled, and validated for LEACH.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.3
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• pp.47-55
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• 2008

본 논문에서는 모바일 ad-hoc 무선 센서 네트워크[1]에서 안정된 경로의 설정 및 설정된 경로의 lifetime 을 효과적으로 지원하여 데이터 전송효율을 향상시키기 위한 협력 도움 라우팅 프로토콜(CARP: Cooperative_Aided Routing Protocol) 을 제안한다. 제안된 라우팅 프로토콜의 기본 아이디어 및 특징은 다음과 같다. 첫째, 소스노드와 목적지 노드 사이의 안정된 라우팅 경로의 설정이다. 본 연구에서는 모바일 노드들의 이동성 정보를 이용한 엔트로피 기반의 안정된 경로 설정방법을 제안 사용한다. 둘째, 협력도움 전송 방법이다[3][4][5]. 설정된 경로 위로 데이터 패킷을 전송 할 때 경로 lifetime과 SNR의 효과적인 지원으로 데이터 전송률을 증가시키기 위해 이웃 노드들로부터 협력 도움을 받는다. 셋째, 기존의 센서 네트워크는 주로 고정된 노드 환경에서 많은 연구가 되어 왔지만, 본 연구에서는 노드들의 이동성을 고려한 환경에서 연구가 이루어진다. 제안된 CARP 의 성능평가는 OPNET(Optimized Network Engineering Tool)을 사용하여 이루어졌으며 성능평가를 통하여 제안한 프로토콜은 안정된 경로의 설정 및 데이터 전송효율을 효과적으로 증가 시킬 수 있음을 알 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.11
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• pp.3008-3025
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• 2012

In this paper, the downlink resource allocation of OFDMA system with decode-and-forward (DF) relaying is investigated. A non-convex optimization problem maximizing system throughput with users' satisfaction constraints is formulated with joint relay selection, subcarrier assignment and power allocation. We first transform it to a standard convex problem and then solve it by dual decomposition. In particular, an Optimal resource allocation scheme With Time-sharing (OWT) is proposed with combination of relay selection, subcarrier allocation and power control. Due to its poor adaption to the fast-varying environment, an improved version with subcarrier Monopolization (OWM) is put forward, whose performance promotes about 20% compared with that of OWT in the fast-varying vehicular environment. In fact, OWM is the special case of OWT with binary time-sharing factor and OWT can be seen as the tight upper bound of the OWM. To the best of our knowledge, such algorithms and their relation have not been accurately investigated in cooperative OFDMA networks in the literature. Simulation results show that both the system throughput and the users' satisfaction of the proposed algorithms outperform the traditional ones.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.793-797
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• 2004

Wireless sensor networks use battery-operated computing and sensing devices. And It can be expected to be deployed in an ad hoc networs. MAC is different from traditional wireless MACs such as IEEE 802.11 in almost every way. so self-configuration and power saving in sensor network are very important goals, while per-node fairness and latency are less important. In this paper, so we use a given prototype for efficient energy conservation to reduce power consumtion that is one of the important character in sensor network and compare energy consumption and collision with IEEE 802.11 MAC. finally we conclude the paper and analyze it.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.3
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• pp.239-246
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• 2013

The IEEE 802.15.4 offers standard about PHY and MAC layer and features low power, low bandwidth, and low speed data communication. Because of this reason, IEEE 802.15.4 is only within a limited range such as sensor detection and home network; nevertheless, the research about transmission multimedia data like voice packet through wireless sensor networks is conducted widely. In this paper, we proposed the group communication system based on the sensor network. TDMA/TDD MAC based on the IEEE 802.15.4 PHY for voice communication on the sensor network is designed by improvement existing peer-to-peer voice communication on the sensor network and hardware is implemented for group communication. To measure the quality of designed system, mean opinion score (MOS) is obtained from the experiment and verified by using sine wave method. As a result of an experiment, we expect that a many cases of application solution can be developed using presented system.

• Journal of Sensor Science and Technology
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• v.28 no.1
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• pp.36-40
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• 2019

Energy harvesting is an advantageous technology for wireless sensor networks (WSNs) that dispenses with the need for periodic replacement of batteries. WSNs are composed of numerous sensors for the collection of data and communication; hence, they are important in the Internet of Things (IoT). However, due to low power generation and energy conversion efficiency, harvesting technologies have so far been utilized in limited applications. In this study, a piezoelectric energy harvester was modeled in a vibration environment. This harvester has an oval-shaped configuration as compared to the conventional cantilever-type piezoelectric energy harvester. An analytical model based on an equivalent circuit was developed to appraise the advantages of the oval-shaped piezoelectric energy harvester in which several structural parameters were optimized for higher output performance in given vibration environments. As a result, an oval-shaped energy harvester with an average output power of 2.58 mW at 0.5 g and 60 Hz vibration conditions was developed. These technical approaches provided an opportunity to appreciate the significance of autonomous sensor networks.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.6-10
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• 2015

RF energy harvesting technology is a promising technology for generating the electrical power from ambient RF signal to operate low-power consumption devices(eg. sensor) in wireless communication networks. This paper, motivated by this and building upon existing CR(Cognitive Radio) network model, proposes a optimal control policy for RF energy harvesting CR networks model where secondary users that have low power consumption harvest ambient RF energy from transmission by nearby active primary users, while periodically sensing and opportunistically accessing the licensed spectrum to the primary user's network. We consider that primary users and secondary users are distributed as Poisson point processes and contact with their intended receivers at fixed distances. Finally we can derive the optimal frame duration, transmission power and density of secondary user from the proposed model that can maximize the secondary users's throughput under the given several conditions and suggest future directions of research.