• Proceedings of the Korean Information Science Society Conference
• /
• 2007.10d
• /
• pp.210-214
• /
• 2007

이동 통신망의 다양화와 단말 기술의 발전에 따라 사용자는 여러 망에 동시에 접근할 수 있게 되었다. 그래서 사용자는 데이터 통신을 위하여 상황과 필요에 따라 망을 선택할 수 있다. 또한 지역적으로 다르게 커버하고 있는 다른 망으로의 이동도 지원받을 수 있다. 최근 3GPP, WiMAX같은 이동 통신망 표준화 단체들에서 IP 이동성 제어 기술로 IETF NetLMM WG의 PMIPv6로 채택하고 표준화를 진행하고 있다. PMIPv6는 단말에 독립적인 네트워크 기반 IP 이동성 제어 기술이다. PMIPv6에서는 IP만을 가진 단말이 자신의 이동에 대한 인식 없이 핸드오버를 제공받을 수 있다. 현재 PMIPv6에서 멀티호밍 이슈들을 반영한 라우팅 방안에 대한 연구가 미흡하다. 그러므로 이러한 PMIPv6가 지원되는 도메인에 멀티호밍 될 수 있는 상황에서 이를 네트워크 기반적으로 라우팅하는 방안에 대한 연구가 필요하다. 본 논문에서는 PMIPv6 도메인 간 멀티호밍을 위한 망 기반 지원 방안을 제시한다.

• International Journal of Internet, Broadcasting and Communication
• /
• v.7 no.2
• /
• pp.130-136
• /
• 2015

In this paper, we analyzed the adjacent channel interference of the LTE band 40 defined by 3GPP on the WLAN system based on the Monte-Carlo method, and found the guard band required for compatibility between the two systems. This study have a difference compared to the previous studies about cell radius was determined using Extended Hata Model considering practical environment, interference protection distance related to guard band, and the spectrum emission mask improvement effect for minimizing the interference. Simulation results, for no channel interference compatibility of LTE and WLAN for mobile satellite wireless package system, we can find the need 15MHz guard band at specified spectrum emission mask and 10MHz guard band at assumed spectrum emission mask.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.4
• /
• pp.293-298
• /
• 2003

In this paper. we propose a fast search algorithm for nearest neighbor vector quantization (NNVQ). The proposed algorithm rejects those codewords which can not be the nearest codeword and reduces the search range of codebook. Hence it reduces computational time and complexity in encoding process, while it provides the same SD performance as the conventional full search algorithm. We apply the proposed algorithm to the adaptive multi-rate (AMR) speech coder and a general vector quantizer designed by LBG. algorithm. Simulation results show effectiveness of the proposed algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.7
• /
• pp.2998-3017
• /
• 2018

Massive (large-scale) MIMO (multiple-input multiple-output) is one of the key technologies in next-generation wireless communication systems. This paper proposes a high-performance low-complexity turbo receiver for SC-FDMA (single-carrier frequency-division multiple access) based MMIMO (massive MIMO) systems. Because SC-FDMA technology has the desirable characteristics of OFDMA (orthogonal frequency division multiple access) and the low PAPR (peak-to-average power ratio) of SC transmission schemes, the 3GPP LTE (long-term evolution) has adopted it as the uplink transmission to meet the demand high data rate and low error rate performance. The complexity of computing will be increased greatly in base station with massive MIMO (MMIMO) system. In this paper, a low-complexity adaptive turbo equalization receiver based on normalized minimal symbol-error-rate for MMIMO SC-FDMA system is proposed. The proposed receiver is with low complexity than that of the conventional turbo MMSE (minimum mean square error) equalizer and is also with better bit error rate (BER) performance than that of the conventional adaptive turbo MMSE equalizer. Simulation results confirm the effectiveness of the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.11C
• /
• pp.1045-1051
• /
• 2003

The SOVA, which produces the soft decision value, can be used as a sub-optimum solution for concatenated codes such as turbo codes, since it is computationally efficient compared with the optimum MAP algorithm. In this paper, we propose an efficient implementation of the SOVA used for decoding turbo codes, by reducing the number of calculations for soft decision values and trace-back operations. In order to utilize the memory efficiently, the whole block of turbo codes is divided into several sub-blocks in the proposed algorithm. It is demonstrated that the proposed algorithm requires less computation than the conventional algorithm, while providing the same overall performance.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.7
• /
• pp.48-55
• /
• 2012

Because of increasing complexity in maximum-likelihood (ML) decoding of four of higher antenna scenario, Partial Interference Cancellation (PIC) group decoding could be the perfect solution to reduce the decoding complexity occurs in ML decoding. In this paper, we separate the symbols the users in the layered basis and find the equivalent channel matrix. Based on the equivalent channel matrix we provide the grouping scheme. In our paper, we construct a block wise transmission technique which will achieve the desired code rate and reduce the complexity and provide less transmission time. Finally we show the different grouping performance.

• Electronics and Telecommunications Trends
• /
• v.30 no.1
• /
• pp.94-101
• /
• 2015

이동통신 기반 IoT(Internet of Things) 관련 표준들은 3GPP와 ETSI를 중심으로 제정되어 왔으나 2012년부터 표준의 중복을 회피하고 단일화된 표준을 통해서 IoT 시장을 성장시키고자 oneM2M이라는 국제적 협의체가 구성되었으며, 최근 Release 1 표준을 발표하는 등 IoT 표준을 사실상 주도하고 있다. Mason과 Machina 리서치에 따르면 2020년에는 동시 연결된 M2M(Machine to Machine)/IoT 장치들의 수가 21억개에 달할 것이고, 이것들이 동시에 200억개의 통신 연결을 생성할 것이다. 이런 수많은 장치들을 관리하기 위한 표준으로 OMA(Open Mobile Alliance)에서는 LWM2M(Lightweight M2M)를 제정하였다. 또한 이런 장치들은 센서들과 같이 연산능력과 배터리에 제약이 많아서 이것을 극복할 수 있는 메시지 프로토콜로 IETF에서는 CoAP 표준을 제정하였다. oneM2M에서도 CoAP과 LWM2M 표준을 채택하였고, 이를 기반으로 한 단말과 응용서비스 관리 기능이 확대될 것으로 기대된다. 본고에서는 이동통신 기반 IoT 표준 동향과 LWM2M 기반 단말 관리 규격에 대해 살펴본다.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.11
• /
• pp.2108-2113
• /
• 2010

The Long Term Evolution (LTE) system is based on the Orthogonal Frequency Division Multiplexing (OFDM) and relies its channel estimation on the lattice-type pilot samples in the multipath fading channel environment. The estimation of the channel frequency response (CFR) makes use of the least squares estimate (LSE) for each pilot samples, followed by an interpolation both in time- and in frequency-domain to fill up the channel estimates for subcarriers corresponding to data samples. Any interpolation scheme could be adopted for this purpose. Depending on the requirements of the target system, we may choose a simple linear interpolation or a sophisticated one. For any choice of an interpolation scheme, these is a trade-off between estimation accuracy and numerical cost. For those wireless communication systems based on the OFDM and the preamble-type pilot structure, the DFT-based channel estimation and its variants have been successfully. Yet, it may not be suitable for the lattice-type pilot structure, since the pilot samples are not sufficient to provide an accurate estimate and it is known to be sensitive to the location as well as the length of the time-domain window. In this paper, we propose a simple interpolated based on the upsampling mechanism in the multirate signal processing. The proposed method provides an excellent alternative to the DFT-based methods in terms of numerical cost and accuracy. The performance of the proposed technique is verified on a multipath environment suggested on a 3GPP LTE specification.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.13 no.2
• /
• pp.35-42
• /
• 2017

The TDD LTE MU-MIMO HARQ system is designed and implemented using GPU based on 3GPP Rel.10 standard. The system consists of the DU part of the base station and the terminal using the general computer based on the GeForce GTX TITAN graphics card provided by NIVIDIA, and constructed the part of the RU using USRP N210 provided by Ettus. In the implementation part, SDR standard is applied, so that various communication standards can be compatible with software. The retransmission is implemented by combining the previous data with the retransmission data using Chase Combining among HARQ methods. In order to confirm that the retransmission was successful, the performance evaluation used LLR constellation. First, if there is an error in the data, the LLR value is not distributed at the corresponding position. in this case, a retransmission is performed to chase combine the previously stored error data and retransmitted data. As a result, the LLR value was distributed at the position of the corresponding LLR value per bit. Through this, it can be confirmed that error - free data is formed by using Chase Combining after retransmission.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.8
• /
• pp.1995-2000
• /
• 2014

Patent information, which is generated under a specific, objective rule for a prolonged period of time, has the properties of technology, right, and management. Because of these characteristics of patents, patent analysis is used to identify R&D capacities and performances, and management strategies of a given nation or enterprise. In this paper, we analyze LTE essential patents which are key IPRs for implementing standardized LTE technology and major weapons in a global patent war. Also, we discuss the status of standard patent data, main applicants and standardization trends based on declared in ETSI standard patents. Especially, we analyzed 15,073 patents data which are possible to analyze patent information.