• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.59-69
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• 2018

In this paper, we present a robust beamforming design to tackle the weighted sum-rate maximization (WSRM) problem in a multicell multiple-input multiple-output (MIMO) - non-orthogonal multipleaccess (NOMA) downlink system for 5G wireless communications. This work consider the imperfectchannel state information (CSI) at the base station (BS) by adding uncertainties to channel estimation matrices as the worst-case model i.e., singular value uncertainty model (SVUM). With this observation, the WSRM problem is formulated subject to the transmit power constraints at the BS. The objective problem is known as on-deterministic polynomial (NP) problem which is difficult to solve. We propose an robust beam forming design which establishes on majorization minimization (MM) technique to find the optimal transmit beam forming matrix, as well as efficiently solve the objective problem. In addition, we also propose a joint user clustering and power allocation (JUCPA) algorithm in which the best user pair is selected as a cluster to attain a higher sum-rate. Extensive numerical results are provided to show that the proposed robust beamforming design together with the proposed JUCPA algorithm significantly increases the performance in term of sum-rate as compared with the existing NOMA schemes and the conventional orthogonal multiple access (OMA) scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.1
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• pp.13-22
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• 2004

This paper drives the exact expression of bit error rate(BER) performance for successive interference cancellation(SIC) algorithm against multipath interference components in a high-speed downlink packet access(HSDPA) system of W-CDMA downlink and the BER performance is evaluated by numerical analysis. Numerical results showed that the average BER performance is rapidly saturated in terms of increasing the number of multipath and is revealed significant improvement for improvement Processing gain(PG). For example, the average BER Performance of the SIC algorithm is superior to the performance of conventional scheme by more than 7dB and 1.4dB for processing gain PG=54 and 128 under the two-path channel and average BER=$1.0{\times}10^{-3}$, respectively. This results also indicated that the average BER saturation is occurred at nearly one weight factor which is assigned to pilot and data channels. Likewise, the average BER performance is greatly degraded due to increasing the interference power in proportional to the number of multipath with increasing multicode K. And the smaller multipath fading channel gain is arrived later, the more the average BER performance is improved. The results of performance analysis in this paper indicated that the multipath interference cancellation is required to improve the BER performance in a HSDPA system under multicode for high-speed packet transmission, low spreading factor, and multipath fading channel.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.7
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• pp.68-73
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• 2009

This paper describes design and implementation of a spread spectrum clock generator (SSCG) for the DisplayPort. The proposed architecture generates the spread spectrum clock using a sigma-delta fractional-N PLL. The SSCG uses a digital End order MASH 1-1 sigma-delta modulator and a 9bit Up/Dn counter. By using MASH 1-1 sigma-delta modulator, complexity of circuit and chip area can be reduced. The advantage of sigma-delta modulator is the better control over modulation frequency and spread ratio. The SSCG generates dual clock rates which are 270MHz and 162MHz with 0.25% down-spreading and triangular waveform frequency modulation of 33kHz. The peak power reduction is 11.1dBm at 270MHz. The circuit has been designed and fabricated using in 0.18$\mu$m CMOS technology. The chip occupies 0.620mm$\times$0.780mm. The measurement results show that the fabricated chip satisfies the DispalyPort standard.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.231-241
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• 2004

This paper drives the exact expression of bit error rate(BER) performance for groupwise iterative-multipath interference cancellation(GWI-MPIC) algorithm for cancelling multipath interference components in a coherent high-speed downlink packet access(HSDPA) system of W-CDMA downlink and the BER performance is evaluated by numerical analysis. The performance of GWI-MPIC is compared to the successive interference cancellation(SIC) algorithm for multipath components. From numerical results, the optimal average BER performance of weighting factor ${\beta}$$\_$h/ for interference cancellation is obtained at ‘${\beta}$$\_$h/=0.8’ and then this weighting factor is hereafter applied to other performance analysis. Numerical results showed that the average BER performance of GWI-MPIC algorithm is rapidly degraded at multipath L=6, but is revealed the good performance than that of SIC algorithm in terms of increasing the number of multipath. This results also indicated that the average BER performance is greatly degraded due to increasing interference power more than multicode K=8. The average BER performance of the proposed algorithm is superior to the performance of SIC algorithm about 3 ㏈ for processing gain PG=128 at multipath L=2 and Average BER=1.0${\times}$10$\^$-5/. And also, the results produced good performance in case of linear monotonic reduction of multipath fading channel gain than that of constant channel gain variation, because multipath fading channel gain which is arrived later is small.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.555-564
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• 2016

This paper proposes a time slot allocation scheme for military patrol environments. This proposal comes from analysis of traffic properties in a military patrol environment. In the near future, robots are expected to explore enemy grounds and measure threat, taking the place of human patrol. In order to control such robots, control messages must be extremely accurate. One mistake from the control center could cause a tragedy. Thus, high reliability must be guaranteed. Another goal is to maintain a continual flow of multimedia data sent from patrol robots. That is, QoS (Quality of Service) must be guaranteed. In order to transmit data while fulfilling both attributes, the per-path based centralized TDMA slot allocation scheme is recommended. The control center allocates slots to robots allowing synchronization among robots. Slot allocation collisions can also be avoided. The proposed scheme was verified through the ns-3 simulator. The scheme showed a higher packet delivery ratio than the algorithm in comparison. It also performed with shorter delay time in the downlink traffic transmission scenario than the algorithm in comparison.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.1003-1013
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• 2006

There is a serious problem in an 802.11g VoWLAN (Voice over Wireless LAN) terminal that talk time is less than 30% compared with an 802.11b terminal. It is almost impossible to achieve talk time level of the 802.11b MAC transmission method because IEEE 802.11g uses OFDM modulation, which is a kind of multi-carrier method and OFDM transmission speed is 54 Mbps faster than normal modulation. In this paper, a new concept of a Holdover time as a power saving method during a call with 802.11g terminal is suggested for the first time. Increase in the number of engaged terminals as a result of holdover time causes to QoS problem because of the increase in the number of back-off and then contention window. In this paper, to solve the QoS problem, a new approach is suggested such that when in down lint the sequence number of 802.11 G.711 is analyzed in the MAC of the terminal and then the Hold over time depending on loss rate is changed. Also, consumption of an electric current of 802.11b/g and MAC parameter's performance due to busy traffic caused by increase in the number of terminal are analyzed and then real data using VQT and Airopeek are analyzed.

• Cartoon and Animation Studies
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• s.35
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• pp.291-312
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• 2014

This study is based on the theory of R.Caillois about element of play which is motivated to infant for studying Hangul. The ultimate goal of play has to be accompanied by pleasure. And learning means permanent changes from experiences for the individual's. Play and learning, these two elements are united to the genre of serious game since the GBL (game based learning) was lead. Most importantly, in order to achieve their own Hangul learning is the fun. Coupled with fun and learning has an important issue for flow because concentration is low in infants than adults. In this case study is to know about fun factor has been applied effectively to Hangul serious mobile game. 20 Infant Hangul mobile serious games of Google Android mobile game section were selected as a case study based on more than 10,000 downloads and user's review rate by April 22, 2014. After that is currently available on the market can play a variety of cases of infant learning Hangul from previous research of R.Caillois offers four categories of play. R.Caillois of Agon, Mimicry, Alea, Ilinx have unique characteristics in comparison with its functional characteristics Hangul four are present any role in Hangul serious mobile games. As a result of the cases selected and the rules of the game will include a maximum of two of the most common types of Agon. Each attribute of the play, rather than one single factor is applied to four kinds of game play performance when properties are distributed to experience together gave the best flow. As a result of this study will be a based research for infants Hangul serious mobile game reflects the properties of the elements of a fun game that you want to combine learning.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.902-909
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• 2023

This study evaluated the performance test of a small-sized LTE-Maritime(LTE-M) transceiver that was developed and promoted to expand the use of intelligent maritime traf ic information services led by the Ministry of Oceans and Fisheries with the aim of supporting the prevention of maritime accidents. Accoriding to statistics, approximately 30% of all marine accidents in Korean water occur with ships weighing less than 3 tons. Therefore, the blind spots of maritime safety must be supplemented through the development of small-sized transceivers. The small transceiver may be used in fishing boats that are active near coastal waters and in water leisure equipment near the coastline. Therefore, verifying whether sufficient performance and stable communication quality are provided is necessary, considering the environment of their real usage. In this study, we reviewed the communication quality goals of the LTE-M network and the performance requirements of small-sized transceivers suggested by the Ministry of Oceans and Fisheries, and proposed a test plan to appropriately evaluate the performance of small-sized transceivers. The validity of the proposed test method was verified for six real-sea areas with a high frequency of marine accidents. Consequently, the downlink and uplink transmission speeds of the small-sized LTE-M transceiver showed performances of 9 Mbps or more and 3 Mbps or more, respectively. In addition, using the coverage analysis system, coverage of more than 95% and 100% were confirmed in the intensive management zone (0-30 km) and interesting zone (30-50 km), respectively. The performance evaluation method and test results proposed in this paper are expected to be used as reference materials for verifying the performance of transceivers, contributing to the spread of government-promoted e-navigation services and small-sized transceivers.