• Journal of Institute of Control, Robotics and Systems
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• v.21 no.5
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• pp.490-495
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• 2015

As flying robots are becoming popular, there are increased needs to use themforsuch purposes as parcel delivery, serving in restaurants, and stage performances. To control flying robots such as quad copters, localization is essential. In order to properly position flying robots, many techniques are in development, including IR (infra-red)-based systemswhich catch markers on a flying robot in order that it can position itself. However, this technique demonstrates only short coverage. Furthermore, localization from inertial sensors diverges as time passes. For this reason, this paper suggests a TWR (two-way ranging) based positioning technique. Despite the weaknesses in currently available TWR system, this paper suggests a self-positioning and outlier detection technique in order to provide reliable position information with a faster update rate. The self-positioning system sends a shorter message which reduces wireless traffic. By detecting and removing outlier measurements, a positioning result with better accuracy is acquired. Finally, this paper shows that the suggesting system detects outlierssequentially from less than half the number of anchors in localization system according to the degree of outlier in measurement and the noise level. By performing an outlier algorithm, better positioning accuracy is acquired as shown in the experimental result.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.245-257
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• 2004

Driven by the growing number of the mobile subscribers, efficient channel resource management plays a key role for provisioning multimedia service in the next generation personal communication systems. To reuse limited channel resources, diminishing the coverage areas of cells seems to be the ultimate solution. Thus, however, causes more handover events. To provide seamless connection environment for mobile terminals and applications, this article presents a novel handover scheme called the intelligent channel reservation (ICR) scheme, which exploits the location prediction technologies to accurately reserve channel resources for handover connections. Considering the fact that each mobile terminal has its individual mobility characteristic, the ICR scheme utilizes a channel reserving notification procedure (CRNP) to collect adequate parameters for predicting the future location of individual mobile terminals. These parameters will be utilized by the handover prediction function to estimate the expected handover blocking rate and the expected number of idle channels. Based on the handover prediction estimations, a cost function for calculating the damages from blocking the handover connections and idling channel resources, and a corresponding algorithm for minimizing the cost function are proposed. In addition, a guard channel decision maker (GCDM) determines the appropriate number of guard channels. The experimental results show that the ICR scheme does reduce the handover-blocking rate while keeping the number of idle channels small.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.149-152
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• 2007

The detection of yellow sand dust using satellite has been utilized from various bands from ultraviolet to infrared channels. Among them, Infrared channels have an advantage of detecting aerosols over high reflecting surface as well as during nighttime. Especially, brightness temperature difference between 11 and 12{\mu}m(BTD) was often used to distinguish between water cloud and yellow sand, because Ice and liquid water particles preferentially absorb longer wavelengths while aerosol particles preferentially absorb shorter wavelengths. We have found that the BTD significantly depends on surface temperature, emissivity, and zenith angle and thereby the threshold of BTD. In order to overcome these problems, we have constructed the background brightness temperature threshold of BTD and then subtracted it from BTD. Along with this, we utilized high temporal coverage of geostationary satellite, MTSAT-1R, to verify the reliability of the retrieved signal in conjunction with forecasted wind information. The statistical score test illustrated that this newly developed algorithm showed a promising result for detecting mineral dust by reducing the errors in the current BTD method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3A
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• pp.293-302
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• 2004

Wireless LAN is a rather mature communication technology that connects mobile terminals. A typical wireless LAN system is composed of one AP and more than one terminals, which is called a BSS. Terminals near to an AP can receive high rate data but terminals far from an AP may not receive data with guaranteed high speed rate because received signal strength is weakened. This paper proposes a method to allow high speed data transmission by grouping terminals and using part of wireless terminals as repeaters. We compare and analyze proposed grouping algorithms based on Depth First Search and Breadth First Search via simulations. A grouping algorithm based on Breadth First Search is shown to be more effective in term of efficiency and coverage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.91-99
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• 2011

Several repeater systems are used to enhance the cell coverage to location such as shadow and rural areas in mobile systems. But the general RF repeater solutions are not suitable for high power outdoor environment because it has the weakness such as self oscillation problem With adoption of a adaptive digital filter technology, feedback interference cancellation repeater prevents oscillation by detecting and canceling the unwanted feedback signal between transmission and receiver antenna. In this paper, dual NLMS based interference cancellation method is proposed and the step size adaptation can be implemented by the estimation of the feedback channel Doppler frequency characteristics. The performance of the proposed algorithm is quantified via analysis and simulation for the static and multipath fading feedback channels.

• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1633-1638
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• 1998

In this paper we propose a generic BIST builder for the Embedded Multiple HAM modules in ASICs, The BlST circuitry is automatically generated according to the specification of the target RAM Modules and the applying test algorithms to them. The lJIST is designed using the TOP-DOWN technique and, thus, has the several advantages in the area of the selection of test algorithm, the development of the circuitry, and the reuse of the circuitry, In addition, we have modified the existing serial interiacing approach to obtain smaller additional BlST circuitry and higher fault coverage and better B1ST sharing of the target RAM Modules in ASICs.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.635-642
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• 2012

The Packet radio C2OTM(Command and Control On The Move) for Command, Control and situational awareness in communication environment of current Combat Net Radio Network is required in a relay transmission techniques. This is to assure the reliability of information transfer, and extend Wireless Coverage and overcome Communication obstacles of mountainous terrain. For the reliability of information transmission in tactical environment, Ad hoc Networking is necessary considering communication environment and an appropriate application of error correction. In this study, We propose a on-demand SDR algorithm that is currently being applied the FEC, Golay, Repetition Code. This enhanced relay transfer uses Ack Reply in tactical operating environment of MIL-STD-188-220 Protocol.

• Journal of Communications and Networks
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• v.17 no.2
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• pp.133-144
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• 2015

In this paper, we introduce a system and a set of algorithms for disseminating popular content to a large group of wireless clients spread over a wide area. This area is partitioned into multiple cells and there is a base station in each cell which is able to broadcast to the clients within its radio coverage. Dissemination of information in the proposed system is hybrid in nature: Each base station broadcasts a fraction of information in the form of random linear combinations of data blocks. Then the clients cooperate by exchanging packets to obtain their desired messages while they are moving arbitrarily over the area. In this paper, fundamental trade-offs between the average information delivery completion time at the clients and different parameters of the system such as bandwidth usage by the base stations, average energy consumption by the clients and the popularity of the spread information are studied. Moreover different heuristic algorithms are proposed to control and maintain a balance over these trade-offs. Also, the more complicated case of multiple sessions where each client is interested in an arbitrary subset of sessions is considered and two variants of the basic dissemination algorithm are proposed. The performance of all the proposed algorithms is evaluated via extensive numerical experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.281-289
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• 2009

Wireless relay attracts great attention as a core technology of next generation wireless communication systems since it enables reliable communications and extends cell coverage by supporting shadowed users. In this paper, we Propose transmit power and subcarrier allocation scheme for downlink OFDM systems with multiple decode and forward (DF) relays to increase data rate with fixed bit error rate (BER) and sum power constraint. In simulation results, average data rate based on the proposed schemes are evaluated and compared to that of the other schemes. It is also shown that the performance loss of the proposed scheme is negligible compared to the optimal scheme, while its computational complexity is reduced considerably.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.2
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• pp.383-403
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• 2021

With the development of mobile edge computing (MEC), some late-model application technologies, such as self-driving, augmented reality (AR) and traffic perception, emerge as the times require. Nevertheless, the high-latency and low-reliability of the traditional cloud computing solutions are difficult to meet the requirement of growing smart cars (SCs) with computing-intensive applications. Hence, this paper studies an efficient offloading decision and resource allocation scheme in collaborative vehicular edge computing networks with multiple SCs and multiple MEC servers to reduce latency. To solve this problem with effect, we propose a context-aware offloading strategy based on differential evolution algorithm (DE) by considering vehicle mobility, roadside units (RSUs) coverage, vehicle priority. On this basis, an autoregressive integrated moving average (ARIMA) model is employed to predict idle computing resources according to the base station traffic in different periods. Simulation results demonstrate that the practical performance of the context-aware vehicular task offloading (CAVTO) optimization scheme could reduce the system delay significantly.