• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.836-843
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• 2004

In per survivor processing (PSP) has a better performance than conventional phase offset estimators. But itsdefect is that it has a high complexity. In this paper, we propose the adaptive reduced state estimator (ARSE) algorithm not only to reduce the complexity, but also to have a good performance. The main principle of ARSE is changing the number of estimators dynamically during the decoding process according to the channel condition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.3 no.3
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• pp.331-343
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• 2009

Many types of sensor data exhibit strong correlation in both space and time. Both temporal and spatial suppressions provide opportunities for reducing the energy cost of sensor data collection. Unfortunately, existing clustering algorithms are difficult to utilize the spatial or temporal opportunities, because they just organize clusters based on the distribution of sensor nodes or the network topology but not on the correlation of sensor data. In this paper, we propose a novel clustering algorithm based on the correlation of sensor data. We modify the advertisement sub-phase and TDMA schedule scheme to organize clusters by adjacent sensor nodes which have similar readings. Also, we propose a spatio-temporal suppression scheme for our clustering algorithm. In order to show the superiority of our clustering algorithm, we compare it with the existing suppression algorithms in terms of the lifetime of the sensor network and the size of data which have been collected in the base station. As a result, our experimental results show that the size of data is reduced and the whole network lifetime is prolonged.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.182-185
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• 2003

Temperature distribution and cooling load in binary current lead are analized, occurring fault current at DC Reactor type superconductor fault current limiter. It is assumed that Normal operating current is 300 A and fault current is 3000 A. Unsteady-state temperature distribution and cooling load of brass current lead optimized for 300 A and 1000 A are calculated by numerical method with TDMA. In the result of calculation, temperature increase in the brass current lead optimized for 300 A is higher than that in the brass current lead optimized for 1000 A, but the temperature increase in the brass current lead optimized for 300 A is not serious. Moreover, increase of cooling load in the brass current lead optimized for 300 A is higher than that in the brass current lead optimized for 1000 A, but normal cooling load in the brass current lead optimized for 300 A is lower than that in the brass current lead optimized for 1000 A. Therefore, designing current lead in superconductor fault current limiter had better to optimize for normal operating current.

• Journal of the Korea Society of Computer and Information
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• v.20 no.7
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• pp.33-40
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• 2015

The time slot assignment problem (TSAP) or Satellite Communications scheduling problem (SCSP) for a satellite performs $n{\times}n$ ground station data traffic switching has been known NP-hard problem. This paper suggests $O(n^2)$ time complexity algorithm for TSAP of a satellite that performs $n^2{\times}n^2$ ground station data traffic switching. This problem is more difficult than $n{\times}n$ TSAP as NP-hard problem. Firstly, we compute the average traffic for n-transponder's basic coverage zone and applies ground station exchange method that swap the ground stations until all of the transponders have a average value as possible. Nextly, we transform the D matrix to $D_{LB}$ traffic matrix that sum of rows and columns all of transponders have LB. Finally, we select the maximum traffic of row and column in $D_{LB}$, then decide the duration of kth switch mode to minimum traffic from selected values. The proposed algorithm can be get the optimal solution for experimental data.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.34-41
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• 1998

In this paper, we evaluate synchronization techniques suitable for high-speed ATM satellite communications with a transmission rate of 155Mbit/s, and propose optimal algorithms that improve the tracking performance, where QPSK is selected for a modulation scheme, and the receiver is operated in burst mode. Based on these asumptions, we proposed modified algorithms and architectures for automatic frequency control(AFC), carrier recovery(CR), and symbol timing recovery(STR) for burst acquisition. Analysis is performed under AWGN environments with respect to the number of required symbol, steady-state stability, and hardware implementation for the proposed algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.106-112
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• 2007

A new space-time cooperative communication relaying strategy with assistant or management terminals is proposed in multi-hop wireless communication systems. More than one relaying terminals are included in one cooperative group to share the state information such as frame error rate and channel information. Among the cooperative group, the best ones are selected to send bit information using space-time codes. An implementation for the proposed scheme is also presented using a TDMA cooperative protocol. Receive signal to transmit signal ratio($E_r/E_s$) and computer simulation show the strategy outperform the conventional cooperative system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.6-12
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• 2008

In uplink cable modem link operated in time-division multiple access mode, it is crucial to employ a suitable preamble pattern enabling frame detection, coarse timing/carrier recovery. Preamble pattern based on the constant envelope zero autocorrelation sequence is proposed for the uplink cable modem compliant to the data over cable service interface specification. Frame detection, coarse/fine timing and carrier recovery algorithms suitable for the proposed preamble pattern are also proposed. We check up the performances using numerical results.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.138-146
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• 1999

The viscous flow around a ship hull is calculated by the use of RANS(Reynolds-averaged Navier-Stokes) solver. Reynolds stresses are midelled by using the k-${epsilon}$ turbulence model and the law is applied near the body. Body fitted corrdinates are introduced for the treatment of the complex boundary of the ship hull form and the governing equations in the physical domain transformed into ones in the computational domain. The transformed equations are numerically solved by an employment of FVM(Finite Volume Method). SIMPLE(Semi-Implicit Pressure Linked Equation) method is adopted in the calculation of pressure and the solution of the sidcretized equation is obtained by the line-by-line method with the use of TDMA(Tri-Diagonal Matrix Algorithme). To assure the proprietty of this computing method, HSVA tanker and Dyne hull are calculated ar both model and ship scale Reynolds number. Their reaults of pressure distributions on fore and aft body, axial velocity contours and transverse velocity velocity vectors and viscous resistance coefficients are compared with other's experiments and calculations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.765-768
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• 2001

A universal shipborne automatic identification system(AIS) uses self-organised time division multiple access(SOTDMA). The performance evaluation system of the SOTDMA algorithm for AIS is needed to implement it efficiently. This paper shows the method of designing it. Real ships access the VHF maritime mobile band but in this performance system, several ship objects access the shared memory. Real ships are designed as the object and the wireless communication channel is designed as the shared memory. This system shows several stations are assigned the transmission slot by the SOTDMA algorithm

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.278-287
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• 2012

In this paper, we propose an allocation scheme for variable message packings to increase efficiency of military operation using Link-16 which is well-known for tactical data link by delivering imagery information rapidly. We propose a variable message packing scheme using COC waveform to support variable data rate under some coverage limitation. Variety of message packing makes Link-16 vary transmission rate appropriately for tactical environment. We also propose a allocation scheme to assign message packing to time slot properly. Finally we verify the performance and superiority of proposed ideas by simulations.