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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Korean Institute of Communications and Information Sciences
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The Korean Institute of Communications and Information Sciences
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Volume & Issues
Volume 41, Issue 8 - Aug 2016
Volume 41, Issue 7 - Jul 2016
Volume 41, Issue 6 - Jun 2016
Volume 41, Issue 5 - May 2016
Volume 41, Issue 4 - Apr 2016
Volume 41, Issue 3 - Mar 2016
Volume 41, Issue 2 - Feb 2016
Volume 41, Issue 1 - Jan 2016
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Sparse Channel Estimation Based on Combined Measurements in OFDM Systems
Min, Byeongcheon ; Park, Daeyoung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 1~11
DOI : 10.7840/kics.2015.41.1.1
We investigate compressive sensing techniques to estimate sparse channel in Orthogonal Frequency Division Multiplexing(OFDM) systems. In the case of large channel delay spread, compressive sensing may not be applicable because it is affected by length of measurement vectors. In this paper, we increase length of measurement vector adding pilot information to OFDM data block. The increased measurement vector improves probability of finding path delay set and Mean Squared Error(MSE) performance. Simulation results show that signal recovery performance of a proposed scheme is better than conventional schemes.
The Study of DoA Estimation in Frequency Domain in Automotive Radar System
Choi, Jung-hwan ; Choi, Ji-won ; Kim, Seong-cheol ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 12~22
DOI : 10.7840/kics.2015.41.1.12
Convenience and safety are the key words for the automotive driving and various sensor technologies have been studied for enhanced perception of driving environments. In frequency modulated continuous wave (FMCW) radar systems, single antenna is enough for range and velocity detection of multiple targets. Multiple array antenna is needed for estimating direction of arrival(DoA). Using DoA estimation algorithm in time domain as in the conventional systems, it is difficult to distinguish vehicles lie in the same angle. In order to facilitate the enhanced angle estimation, DoA estimation algorithm is applied in frequency domain. In this paper, the method for applying multiple signal classification(MUSIC) algorithm in frequency domain is suggested and the performance is analyzed.
Allowing a Large Access Timing Offset in OFDM-CDMA Using ZCZ Code and Block Spreading
Na, Donj-jun ; Choi, Kwonhue ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 23~36
DOI : 10.7840/kics.2015.41.1.23
We propose a new type of OFDM-CDMA scheme which allows large inter-user timing offset using zero correlation zone(ZCZ) code in conjunction with block spreading technique. Moreover to maximize spectral efficiency, the proposed OFDMA does not have guard time(GT). This is opposite to the trends in the conventional schemes where GT are supposed to be larger to allow larger inter-user timing offset. It is remarkable that the proposed GT-free OFDM-CDMA scheme completely cancels inter-user interference in the multipath fading simply by despreading process. This inter-user interference-free feature still remains even there exist inter-user timing offsets as large as multiple OFDM symbols. Although the self-user interference exists due to no GT, it can be effectively suppressed by simple successive interference cancellation(SIC) from the first symbol in spread block as it is free from inter symbol interference(ISI).
Localization Techniques Based on Image Sensor and Visible Light Communication
Le, Nam-Tuan ; Ifthekhar, Md. Shareef ; Mondal, Ratan Kumar ; Jang, Yeong Min ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 37~41
DOI : 10.7840/kics.2015.41.1.37
Localization is one of the key issues of demandable applications, especially smart services. Beside the traditional GPS based localization technique, the localization issue by visible light communications is promising market because of possibility of combining visible light communications with positioning technique for a high accurate, especially indoor localization service. This paper provides the overview and new image sensor scheme for localization issue based on visible light communication. The survey is introduced from core techniques to enhancement issues of localization. We hope these will be the essential references for the impact selection method in implementation and standardization issues.
The Determination of Multiplexing-Diversity Transition Mode in the Visual-MIMO System
Kim, Ji-won ; Kim, Ki-doo ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 42~50
DOI : 10.7840/kics.2015.41.1.42
Recently, researches about the communication between LED array and the camera (alias `Visual-MIMO`), have been actively conducted, and the application to the vehicle and a smart phone is expected to be maximized. Since the bit error may occur if the ISI is severe in a LED array, it is necessary to switch from the multiplexing to the diversity mode. In this paper, according to the use or not of a reference array pattern, a method for determining the transition time to the diversity mode is suggested and verified. When using the reference pattern, it determines the transition time to the diversity mode from the multiplexing using the brightness information of the received image. If the reference array pattern is not used, the size of LED array compared to the entire image according to the distance is used and the size of the LED array at the distance of a severe ISI may be used for the determination of transition time to the diversity. Finally, the proposed method is verified through the simulation and hardware experiments as well as by analyzing the performance in accordance with the ISI level and the distance.
Physical Layer Modem Implementation for mmWave 5G Mobile Communication
Kim, Jun-woo ; Bang, Young-jo ; Park, Youn-ok ; Kim, Ilgyu ; Kim, Tae Joong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 51~57
DOI : 10.7840/kics.2015.41.1.51
This paper describes the physical layer modem structure of Giga KOREA 5G system which is being developed by ETRI as a 5G telecommunications prototype. The objective of Giga KOREA 5G system is supporting maximum 100 Gbps data rate for each cell with wide-bandwidth baseband station and mobile station prototypes in mmWave (10~40 GHz) environment. To achieve this objective, its physical layer is composed of high performance baseband station as well as mobile station and their OFDM TDD modems. The important features of Giga KOREA 5G physical layer are carrier aggregation, multiple receiving beam searching in mobile station, high data rate channel encoder and decoder and high speed modulation and demodulation functions.
Performance Evaluation of PEP Based on Cross-Layer in Satellite Communication System
Kim, Jong-Mu ; Nathnael, Gebregziabher W. ; Lee, Kyu-Hyan ; Kim, Jae-Hyun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 58~65
DOI : 10.7840/kics.2015.41.1.58
Satellite communication is a wide area network (WAN) which provides communication service worldwide. However, the performance of TCP can be seriously degraded in the satellite networks due to limited bandwidth, long round-trip time (RTT) and high bit error rate (BER) over satellite links. In order to improve the performance of TCP, this paper proposes cross-layer Performance Enhancing Proxy (PEP) in digital video broadcasting-return channel via satellite (DVB-RCS) networks. The proposed protocol sets TCP Congestion Window (CWND) size by using satellite resource allocation information exchanged between TCP and the link-layer. we implement PEP testbed based on Linux to evaluate the performance of the proposed protocol. The simulation results show that the proposed protocol performs better than standard TCP both in single and multiple sessions in variant BER, because the proposed protocol sets TCP CWND size by using satellite resource allocation.
New Hierarchical Modulation Scheme Using a Constellation Rotation Method
Kim, Hojun ; Shang, Yulong ; Park, Jaehyung ; Jung, Taejin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 66~76
DOI : 10.7840/kics.2015.41.1.66
In this paper, we propose a new hierarchical modulation scheme for DVB-NGH to improve the performance of LP (Low-Parity) signals by applying a conventional constellation-rotation method to the LP signals without virtually a loss of performance of a HP (High-Parity) signals. The improvement of the LP signals is mainly due to the increased divesity gain caused by the constellation-rotation method which barely affect the performance of the HP signals. For the new scheme, we also propose a hardware-efficient ML (Maximum-Likelihood) detection algorithm that first decodes the HP signals by using a conventional HP receiver, and then simply decodes the precoded LP signals based on the pre-detected HP signals.
Normalization Factor for Three-Level Hierarchical 64QAM Scheme
You, Dongho ; Kim, Dong Ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 77~79
DOI : 10.7840/kics.2015.41.1.77
In this paper, we consider hierarchical modulation (HM), which has been widely exploited in digital broadcasting systems. In HM, each independent data stream is mapped to the modulation symbol with different transmission power and normalization factors of conventional M-QAM cannot be used. In this paper, we derive the method and formula for exact normalization factor of three-level hierarchical 64QAM.
Performance Evaluation of De/Modulations for ULP Communications for WPAN Systems
Kim, Yongok ; Jang, Youngrok ; Choi, Sooyong ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 80~82
DOI : 10.7840/kics.2015.41.1.80
In this letter, we evaluate the performances of both GOOK and GFSK de/modulation techniques which are candidates for ULP communications in WPAN systems. For the performance evaluation, we define the system model for each of GOOK and GFSK de/modulations and perform computer simulations based on the proposed models. From the computer simulations, we show that GOOK de/modulation technique has 15 dB out-of-band emission gain and is robust over frequency offsets in terms of BER compared to GFSK de/modulation technique.
Regularized LS Signal Detection for OFDM in Fast Time Varying Channels
Lim, Dongmin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 83~85
DOI : 10.7840/kics.2015.41.1.83
The OFDM with LS signal detection performs worse in fast time varying channels as the channel matrix has higher chance of becoming ill-conditioned. Various regularization methods are applied to avoid performance degradation in LS signal detection. In this paper, we proposed a CGLS method with the stopping criteria imposed by the characteristics of the modulation method, which shows performance comparable to that of the optimal LMMSE.
Reducing Transmission Errors on The Report Channel for Simultaneous Reporting Based Cooperative Spectrum Sensing
Lim, Chang Heon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 86~88
DOI : 10.7840/kics.2015.41.1.86
In a previous work, a simultaneous reporting scheme for cooperative spectrum sensing has been presented for a resource efficient transmission over a report channel. In this paper, we present a method of reducing transmission errors on the report channel for it and evaluate its performance by simulation.
SIM/SM Optical Wireless Communication System with Higher Modulation
Lee, Seong-hee ; Hwang, Seung-hoon ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 89~91
DOI : 10.7840/kics.2015.41.1.89
This paper proposes the method of applying higher modulation in order to improve data rate of the system combining SM with SIM in Optical wireless communication.
Analysis of VoLTE Charge Reduction under VoLTE Growth
Lee, Sang-Woo ; Jeong, Seon-Hwa ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 92~100
DOI : 10.7840/kics.2015.41.1.92
It is informed that the Voice over LTE(VoLTE) which serves voice and message on IP networks is better in terms of economies of scale than the legacy voice service on 2G/3G circuit-switched networks because of its technological and cost efficiency. In addition, services of voice and data are running on a single LTE network and as a result VoLTE has the more economies of scope. But, there is no study about how much technology-efficiency VoLTE has compared to circuit-based voice service and how much voice charge can be reduced as VoLTE grows up. This paper analyzes empirically cost-efficiency of VoLTE against circuit-based voice service and quantifies the reduction of voice charge as 2G/3G voice traffic shifts to VoLTE. The results describe the first is that the average cost of the total voice traffic rises shortly just after the investment of LTE network for providing VoLTE but it will soon have a capacity available to reduce the charge due to VoLTE`s outstanding cost efficiency on the assumption that voice traffic is fixed, and the second is that the charge can be cut to 60% of the current rate in case of all the voice traffic moves to VoLTE. The latter proves partially the validation of data-focusing pricing plan. Our results are expected to become basic data for network operators` establishing pricing strategies and for policy makers` inducing price cutting.
Cookie-Based Identification of the Public Keys of TLS/SSL Certificates
Park, Jun-Cheol ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 101~103
DOI : 10.7840/kics.2015.41.1.101
We propose a HTTP cookie-based identification of the public keys of Web sites for the case of failure to validate certificates. The proposed scheme effectively protects users from the phishing attacks of inducing them to access bogus sites. It incurs little performance overhead on the browser and the server of Web sites. It requires to implement the input processing of user credentials and the encryption and verification of cookie values, though.
Slotted ALOHA with Variable Slot Length for Underwater Acoustic Systems
Lee, Junman ; Kang, Chung G. ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 104~106
DOI : 10.7840/kics.2015.41.1.104
In this letter, we consider a random access scheme for underwater acoustic network, in which a slotted ALOHA with variable slot length is designed to enhance the random access performance for the nodes with the varying propagation delay.
Impact of Periodic Channel Scanning on the TCP Throughput in a WLAN
Hwang, Jaeryong ; Choi, Jaehyuk ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 107~109
DOI : 10.7840/kics.2015.41.1.107
In this paper, we address the TCP-over-WLAN performance problem that occurs during periodic active background scanning with which mobile devices discover available APs in the vicinity. We measure the impact of the scanning period on the TCP throughput and observe a significant performance degradation when the scan operation period is shortened. Our experimental analysis has identified the main cause of the problem, that is, the associated AP continues to send packets to the mobile device even when the device is not able to receive due to the scanning operation.
Group-Based Frequency Hopping Scheme for Improving Multi-Net Performance of Link-16 Waveform with Limited Frequency Band
Yu, Jepung ; Lee, Kyuman ; Baek, Hoki ; Lim, Jaesung ; Kim, Jongsung ; Choi, Hyogi ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 110~121
DOI : 10.7840/kics.2015.41.1.110
Link-16 is a representative TDL operated by US air force and NATO and supports structure of Multi-net. Under Multi-net, military operation can be conducted effectively since terminal nodes in Link-16 hop over total frequency band simultaneously. As air traffic is rapidly increasing, new aeronautical system is introduced or existing system should be expanded to accommodate increasing air traffic and frequency band assigned for operating this system is scarce. It is scheduled to implement frequency remapping to solve frequency scarcity. With limited frequency band for operating Link-16, as frequency remapping is implemented, degradation of Multi-net performance can happen since multiple access interference in Link-16 is increasing so it is difficult to conduct multiple military operations. Thus, Group-based frequency hopping scheme is proposed to solve this problem. We verified the performance of the proposed scheme is improved.
Identification of Voice for Listeners who Feel Favor Using Voice Analysis
Choi, Ji Hyun ; Cho, Dong Uk ; Jeong, Yeon Man ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 122~131
DOI : 10.7840/kics.2015.41.1.122
In the smart societies, such as the current unlike in the past, the voice that listeners will feel favor is changing through the development of ICT technologies and infrastructure. In other words, in the past, loud, intensive and fast voice is a favorite but now a new social and cultural situation that is changing them with ICT technologies. Now, this becomes one of the important things that we clarify `Is it a voice that feels a favor?`. For this, in this paper, we identified what voice that listeners feel favor by applying ICT technologies. Studies were carried out to proceed largely divided into two categories. Firstly, as the quantified data, we extracted the impact on favorable feeling of listeners which related with emotional speech by empirical analysis work. To do this, we performed the experiment for the public. Secondly, we identified what kind of voice which listeners feel a good impression. For this, we identified voice characteristics that there are people who are influential in the real society. Also, we extracted both the voice characteristics of each influential people and common voice characteristics. In addition, we want to overcome the problems of qualitative methods that have originally limitations in objective respects which is significant to the voice analysis. For this, we performed the experiments of the voice analysis by numerical and visual approaches.
Underwater Channel Environment Analysis Using 10Khz Carrier Frequency at the Shore of West Sea
Kim, Min-sang ; Ko, Hak-lim ; Kim, Kye-won ; Lee, Tae-seok ; Im, Tae-ho ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 132~139
DOI : 10.7840/kics.2015.41.1.132
This study was carried out near the waters of Jango port, Dangjin-gun, Chungcheongnam-do by utilizing 10kHz carrier frequency, for the purpose of measurement and analysis of underwater channel environment of the Western sea. For the measurement of horizontal channel environment, the separation distance between transmitter and receiver is made differently in the range between 10m and 4000m. Meanwhile, for the measurement of vertical channel environment, transmission and receiving side ships are fixed as contacted each other and measured differently depending on their depth of submergence. In this study, the Coherence Bandwidth and the Coherence Time were estimated by analyzing the Power delay profile of the real sea based on the measured data, and analyzing the doppler frequency through frequency conversion of received tone-signal, respectively. This study is expected to become a base study in carrying out the frame design for underwater communication to improve the communication and secure the reliability of communication in future underwater channel environment.
Key Techniques and Performance Comparison of 5G New Waveform Technologies
Kang, Hyeon Su ; Song, Young Bae ; Kwon, Doyle ; Kim, Duk Kyung ;
The Journal of Korean Institute of Communications and Information Sciences, volume 41, issue 1, 2016, Pages 142~155
DOI : 10.7840/kics.2015.41.1.142
In order to satisfy 5th generation mobile system`s requirements, recently many works have been done in various layers. Especially in physical layer, new waveforms like Filter bank Multi-Carrier(FBMC), Universal Filtered Multi-Carrier(UFMC), Generalized Frequency Division Multiplexing(GFDM) have been proposed and their performance have been evaluated. But most previous researches have provided limited information by comparing couple new waveforms each other with different assumptions and simulation parameters. In this paper, we investigate the key technique of each 5G new waveform, and compare them in various aspects and the same simulation environment, and finally provide what waveform is appropriate in different application scenarios.