• 한국신뢰성학회지:신뢰성응용연구
• /
• 제5권4호
• /
• pp.465-486
• /
• 2005

A unreliable network system results in unsatisfied performance. A performance criterion of a network is throughput and availability. One of the most compelling technological advances of this decade has been the advent of deploying wireless networks of heterogeneous smart sensor nodes for complex information gathering tasks, The advancement and popularization of wireless communication technologies make more efficiency to network devices with wireless technology than with wired technology. Recently, the research of wireless sensor network has been drawing much attentions. In this paper, We evaluate throughput and availability of wireless sensor network, which have hierarchical structure based on clustering and estimate the maximum hroughput, average throughput and availability of the network considering several link failure patterns likely to happen at a cluster consisted of sensor nodes. Also increasing a number of sensor nodes in a cluster, We analysis the average throughput and availability of the network.

• ETRI Journal
• /
• 제34권1호
• /
• pp.9-16
• /
• 2012

Precoding in the multiple-input multiple-output orthogonal frequency division multiplexing system is investigated. In conventional wideband precoding (WBP), only one precoder, obtained from the decomposition of the subcarrier independent channel matrix, is used for all subcarriers. With an investigation of the relationship between the subcarrier independent channel matrix and the temporal/frequency channels, an improved WBP scheme is proposed for practical scenarios in which a part of subcarriers are allocated to a user. The improved WBP scheme is a generalized scheme of which narrow-band precoding and conventional WBP schemes are special modes. Simulation results demonstrate that the improved WBP scheme almost achieves the optimum performance of a single precoder and outperforms the conventional WBP scheme in terms of the bit error ratio and ergodic capacity with slight complexity increase. The largest advantage of the improved WBP scheme on signal-to-noise ratio in simulation results is over 2.1 dB.

• 한국통신학회논문지
• /
• 제33권2A호
• /
• pp.198-203
• /
• 2008

In this paper, we consider the diffuse type of indoor wireless optical communication (WOC) system. To find the channel characteristics of indoor wireless infrared communication system, we investigate the simulation process to get the impulse response of diffuse type and analyze the scenario of the indoor structure which we have built. The simulation results of the impulse response include power ratio and time delay due to bounce times. We get and discuss the receiving power distribution according to six configurations which have different transmitter and receiver positions and reflection coefficients of the indoor structure assumed. The results of this paper are useful to design the indoor wireless optical communication systems.

• 한국정보기술학회 영문논문지
• /
• 제9권1호
• /
• pp.25-37
• /
• 2019

Power-line communication (PLC) has influenced smart grid development. In addition, PLC has also been instrumental in current research on internet-of-things (IoT). Due to the implementation of PLC in smart grid and IoT environments, strides have been made in PLC and its combination with the wireless system to form a hybrid communication system. Also, PLC has evolved from a single-input-single-output (SISO) configuration to multiple-input-multiple-output (MIMO) configuration system, and from a point-to-point communication system to cooperative communication systems. In this work, we extend a MIMO wireless two-way amplify-and-forward (AF) cooperative communication system to a hybrid PLC and wireless (PLC/W) system configuration. We then maximize the weighted sum-rate for the hybrid PLC/W by optimizing the precoders at each node within the hybrid PLC/W system. The sum-rate problem was found to be non-convex, therefore, an iterative algorithm is used to find the optimal precoders that locally maximize the system sum-rate. For our simulation results, we compare our proposed hybrid PLC/W configuration to a PLC only and wireless only configuration at each node. Due to an improvement in system diversity, the hybrid PLC/W configuration outperformed the PLC only and wireless only system configurations in all simulation results presented in this paper.

• Journal of information and communication convergence engineering
• /
• 제1권1호
• /
• pp.35-38
• /
• 2003

Analyses of performance of wireless broadband communication systems employing fiber-optic link have presented. We have analyzed CNR penalty to evaluate system performance by taking into account, radio link considering rainfall attenuation, and optical link considering several carrier-to-noise ratio versus the optical modulation index.

• 제어로봇시스템학회논문지
• /
• 제6권8호
• /
• pp.652-658
• /
• 2000

Wired and wireless communication technique is growing rapidly. As the number of communication users is larger problems such as network congestion and signal interference between users are getting most important, There have been researches that try to solve them by control theoretic approaches. They apply various control theories to the control issues of communication. this paper surveys these researches and classifies them into ATM TCP/IP and wireless communication according to the target. The feedback control model of each communication protocol is shown and related researches are summarized and analyzed.

• International Journal of Advanced Culture Technology
• /
• 제9권4호
• /
• pp.409-416
• /
• 2021

We are invented the movement composition technique that is to check the food adjacent-package status of the wireless-management movement monitoring level (WMMML) on the movement monitoring communication system. The movement monitoring level condition by the movement monitoring communication system is formatted with the adjacent-package system. As to inspection a wireless RFID of the wireless RFID, we are found of the movement value with wireless RFID by the adjacent upper take form. The concept of movement monitoring level is formatted the reference of wireless-management level for composition signal by the movement package communication system. Further symbolizing a food composition of the WMMML of the medium-minimum in terms of the adjacent-package communication system, and the movement wireless RFID package that was the movement value of the far composition of the Mo-MMCS-FA-_φMED-MIN with 5.80±1.20 units, that was the movement value of the convenient composition of the Mo-MMCS-CO-_φMED-MIN with 4.06±(-0.04) units, that was the movement value of the flank composition of the Mo-MMCS-MO-_φMED-MIN with 0.91±0.07 units, that was the movement value of the vicinage composition of the Mo-MMCS-VI-_φMED-MIN with 0.18±(-0.03) units. The adjacent package will be to look into at the food ability of the adjacent-package communication system with wireless RFID by the movement monitoring level on the WMMML that is supply the wireless communication by the movement monitoring level system. We will be possible to make effort of a communication system by the management signal and to put to use of the delivery data of RFID level by the delivery system.

• International Journal of Contents
• /
• 제12권1호
• /
• pp.65-69
• /
• 2016

Wireless communication chipsets have fixed transmission rate and communication distance. Although there are many kinds of chipsets with throughput and distance purpose, they cannot support various types of wireless applications. This paper provides theoretic research results in order to support various wireless applications requiring different throughput, delayed quality-of-service (QoS), and different communication distances by using a wireless communication chipset with fixed rate and transmission power. As a performance metric, the probability for a data frame that successfully receives at a desired receiver is adopted. Based on this probability, the average number of transmission in order to make a successful frame transmission is derived. Equations are utilized to analyze the performance of a single-hop with channel coding and a dual-hop without error correction matter transmission system. Our results revealed that single-hop transmission assisted by channel coding could extend its communication distance. However, communication range extending effect of the single-hop system was limited. Accordingly, dual-hop transmission is needed to overcome the communication distance limit of a chipset.

• 한국통신학회논문지
• /
• 제29권2B호
• /
• pp.151-157
• /
• 2004

본 논문은 밀리미터파 대역용 무선통신송수신기를 이용하여 도시환경에 적합한 초고속무선통신 셀백본망을 구축하는 것에 관한 것이다. 밀리미터파 대역중 산소분자의 신호흡수 특성이 큰 60㎓ 대역용 무선통신송수신기를 제작하였으며, 이를 이용한 통신시스템간의 간섭신호가 제거되고 망구성의 형태에 따른 다양한 무선링크의 유효거리를 확보할 수 있음을 확인하였다. 또한 무선백본노드를 중심으로 유효반경 약 500m에서 3km이내의 셀간격으로 각각의 서비스망을 구축하여 도시전체를 셀망의 무선백본망을 구성하고, 155.52MbpsATM(OC-3)급의 도시형 무선 통신 셀백본망이 가능토록 하였다.

• ETRI Journal
• /
• 제41권2호
• /
• pp.224-234
• /
• 2019

This paper proposes a new spectrum forecasting (SF) model to estimate the spectrum demands for future mobile broadband (MBB) services. The model requires five main input metrics, that is, the current available spectrum, site number growth, mobile data traffic growth, average network utilization, and spectrum efficiency growth. Using the proposed SF model, the future MBB spectrum demand for Malaysia in 2020 is forecasted based on the input market data of four major mobile telecommunication operators represented by A-D, which account for approximately 95% of the local mobile market share. Statistical data to generate the five input metrics were obtained from prominent agencies, such as the Malaysian Communications and Multimedia Commission, OpenSignal, Analysys Mason, GSMA, and Huawei. Our forecasting results indicate that by 2020, Malaysia would require approximately 307 MHz of additional spectrum to fulfill the enormous increase in mobile broadband data demands.