• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.9
• /
• pp.1-9
• /
• 2011

In this paper, we propose an efficient method to create clusters of geographically distributed base stations which cooperatively transmit signals in cellular mobile communication systems. The proposed method utilizes a sequential selection approach to choose candidate base stations which can provide maximum weighted sum-rate gain when they participate in the cooperative transmission with the existing cluster. In particular, the proposed method limits the maximum number of base stations in a cluster by considering the system operational and implementation complexities. Moreover, the combinations of clusters dynamically change along with variations of channel environments. Through computer simulations, performance of the proposed method is verified by comparing with the non-cooperative transmission method and the static clustering method. Numerical result shows that the proposed sequential selection based clustering method is especially advantageous for the performance improvement of lower percentile users in terms of average throughput, and thus the proposed method can effectively improve the fairness among users.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.12
• /
• pp.2614-2618
• /
• 2012

Recently, multimedia broadcasting traffic is explosively increasing since the performance of smartphones is significantly enhanced and capacity of mobile access network such as LTE is steeply increasing. We can accommodate the multimedia broadcasting traffic via general unicast scheme or eMBMS which is a broadcast-specific scheme. First, the unicast scheme provides higher spectral efficiency compared to the eMBMS. However, unfortunately, the efficiency of the unicast scheme dramatically decreases as the number of users increases. On the other hand, although the spectral efficiency of the eMBMS is lower than that of the unicast, it can serve many users with a channel. Thus, this paper defines and investigates the capacity efficiencies of the both schemes for multimedia broadcasting traffic. In addition, we derive the optimal number of users where the eMBMS can provide the higher capacity efficiency than that of the unicast scheme.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.12B
• /
• pp.1076-1086
• /
• 2006

In providing video-on-demand (VoD) services to a number of clients through networks, the bandwidth requirements of video transmission restrict VoD services. For this reason, many significant broadcasting-based VoD schemes have been proposed to efficiently support services. However, the broadcasting-based VoD schemes approach needs frequency channel hopping, using many channels at the same time and managing many segments of a video. These make it difficult to implement. In this paper, we propose a Harmonic Staggered broadcasting scheme which has a simple structure and substantially improved VoD efficiency. The numerical results demonstrate that the viewer's waiting time of the Harmonic Staggered broadcasting scheme is close to the harmonic broadcasting scheme and the maximum buffer requirements of this can be adapted for demanding rate by adjusting the short front part of a video sizes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.05a
• /
• pp.741-744
• /
• 2001

In this study, a OFDM mode, unlike traditional single carrier mode, is that a great number of carrier in multi-channel environment is transmitted by modulating objective Data parallel in order to execute high speed Data translation and make frequency orthogonal to offer high spectrum efficiency. As a result, this method is adopted to a variety of fields and is being actively studied. In this papers, the efficiency of OFDM wireless-communication systems is evaluated by modulation methods through computer simulation. M-PSK and M-QAM are used as modulation methods. The simulation is executed in a real channel and a virtual channel included multi-path, AWGN, Peak Power clipping, Frame Start Time Error As a result of simulation, it is confirmed that M-QAM method is superior to M-PSK in OFDM systems in terms of the transmission methods.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.37 no.1
• /
• pp.58-62
• /
• 2000

We Propose modulation scheme using I-Q modulation for transmitting different information simultaneously. For transmitting 1bit of each information, we apply QPSK scheme, for more bits, MAPSK. At the second modulation stage, We mix PN wavefoms with APSK waveforms for spreading bandwith. BER(Bit Error Rate) of each Information of the proposed scheme is analyzed on computer simulation. Finally we show power spectrum before and after spreading bandwidth.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.723-726
• /
• 2005

GALS (Globally Asynchronous Locally Synchronous) 시스템 기반의 SoC 설계에 필수적인 DI (Delay Insensitive) 데이터 전송방식 중 기존의 전압 모드 기반 설계 방식은 N 비트 데이터 전송에 물리적으로 2N+1 개의 도선이 필요하다. 이로 인한 전력 소모와 설계 복잡성을 줄이기 위해 N+1 개의 도선으로 N 비트 데이터를 전송할 수 있는 전류 모드 다치 논리 회로 기반 설계 방식이 연구되었다. 그러나, static 전력의 비중이 커 데이터 전송 속도가 낮을수록 전력 소모 측면에서 취약하고, 휴지 모드에서도 상당량의 전력을 소비한다. 본 논문에서는 이러한 문제점을 해결할 수 있는 전류 모드 기반 인코더와 디코더 회로를 제안하고, 이에 따른 새로운 전류 인코딩 기법을 설명한다. 마지막으로 기존의 전압 모드 및 전류 모드 방식과 delay, 전력 소비 측면에서 비교 데이터를 제시한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2012.07a
• /
• pp.242-245
• /
• 2012

본 보고서는 지상파방송 디지털 전환 과정에서 아직 전송방식조차 선정하지 못하고 있는 라디오의 디지털화 추진과 관련하여 AM 라디오의 DRM 전송방식에 의한 실험방송 조기 추진의 필요성과 의미를 설명하고, FM의 디지털화 역시 DRM+ 전송방식 중심으로 TV채널 5번과 6번 LOW-VHF 밴드 주파수 대역에서의 OUT-OF-BAND 방법으로 검토해 봄으로써 기존 FM송신기 및 안테나와 콤바인이 쉽고 우수한 신호 전달력을 가진 LOW-VHF대역 주파수를 효과적으로 활용할 수 있으며 각 사업자별로 출력지정과 권역설정이 자유로워 디지털시대에 맞는 새로운 서비스 환경 구축과 AM/FM대역 동일방식 디지털 라디오 보급을 할 수 있는 특징으로 인해 라디오의 디지털화 추진에 유리한 방안임을 확인해 보고자 한다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.7
• /
• pp.1394-1399
• /
• 2007

In this paper we propose a Hybrid MAC(HMAC) to enhance the transmission throughput in Wireless Sensor Networks(WSNs). In the proposed HMAC, sender nodes send transmission request packets to the receiver nodes using CSMA/CA MAC protocol. And the receiver node assigns slots according to the network topology and the amount of traffics using TDMA. Using HMAC we get the enhanced throughput by lowering the duplicated slot assignment.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.15 no.3
• /
• pp.445-450
• /
• 2020

Cooperative networks provides the benefits of performance improvements and capacity increment when the source node transmits signal to the destination node using several relay nodes. In this paper, we consider the cooperative network where the transmission scheme between the source node and relay node use conventional binary signaling, whereas the transmission scheme between thee relay node and destination node adopt the differential space time coding signaling. We analyze the performance of the system depending on the modulation scheme, i.e., coherent and differential modulation, at the source-relay links. The performance depending on the relay location is also compared by considering modulation scheme and the number of relay node.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2015.05a
• /
• pp.97-100
• /
• 2015

In this paper, we propose an efficient method of transmitting data according to size using the Zigbee and Wifi in a wireless sensor network. In existing wireless sensor network using Zigbee and Wifi, Zigbee transmits text and Wifi transmits image and video. Existing research methods in this way is caused a problem that the transmission by selecting a transmission method according to data type. In the case of aggregated data, Zigbee is less efficient than Wifi in some case because of limitation of zigbee's transmission rate, even if data type is text. In this paper, we propose a method for selecting a transmission method by considering the size of the data and transfer efficiency not by data type. It was obtained results that appear to be convenient, according to the linkage algorithm structure of the image and sensing data by selecting a transmission method from data size, not the type of the given data.