• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.3
• /
• pp.25-31
• /
• 2015

In this paper, we propose PEP based on cross-layer and network coding in digital video broadcasting-return channel via satellite (DVB-RCS) networks. In particular, we propose not only a scheme of cross-layer information exchange for interaction between TCP and the resource allocation (RA) scheme in the link layer but also a tuning algorithm for the TCP contention window (CWND) by using information on the RA in the link layer and the redundancy rate for network-coded packets. The simulation results show that TCP CWND can be adjusted by RA information in the proposed protocol. Furthermore, through the transmission of network-coded packets and the proposed CWND tuning algorithm, TCP throughput is enhanced in lossy environment due to user mobility without the unnecessary resource overhead.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.2
• /
• pp.176-187
• /
• 2002

The digital Audio Broadcasting (DAB) system adopts Coded OFDM(COFDM) for channel coding. The COFDM is a combined technique of multicarrier transmission(OFDM) and punctured convolutional coding with viterbi error correction. Because the channel coding is an important topic for OFDM systems, this paper proposes a new turbo coded OFDM system that replaces the existing RCPC codec by a turbo codec without modifying the puncturing procedure and puncturing vectors defined in the standard DAB system for compatibility. The performance of a new system is compared to that of the conventional system under the frequency selective Rician fading channel and the frequency selective Rayleigh fading channel in conjunction with DAB transmission mode I suitable for the terrestrial single frequency network(SFN) broadcasting. The standard system's performance was improved with the aid of turbo codec.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5C
• /
• pp.351-360
• /
• 2008

In cellular mobile radio systems with frequency reuse, the interference signals degrade the channel estimation and signal detection performance due to the low signal-to-interference ratio near coverage boundaries. When the preamble pilot sequences from different cells are orthogonal or located in disjointed positions, they can be used for multi-cell channel estimation and interference cancellation. In time-varying channels caused by Doppler spread, data pilot symbols are needed for channel estimations. However, data pilot symbols are usually located in identical positions for the overhead reduction, which degrades the channel estimation performance. In this paper, we demonstrate a significant amount of performance improvement is achieved by multiplying different pseudonoise(PN) sequences to the data pilot symbols from adjacent interference cells. In particular, for detection scheme using maximal ratio combining(MRC) and inter-cell spatial demultiplexing(ISD), quantitative performance gain of spectral efficiency for different values of Doppler frequency and interference power is presented.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.12
• /
• pp.2800-2804
• /
• 2015

Recently, device-to-device (D2D) direct communication is attracting much interest and many researches have been conducted. In this paper, we investigated an algorithm to support the D2D direct communication in cellular mobile communication networks. We investigated the optimal D2D scheduling algorithm which can achieve the maximal sum-rate in cellular uplink frequency. We also proposed a simple scheduling algorithm which can considerably reduce the computational complexity, compared to the optimal scheme. Finally, we analyzed the performance of the proposed scheme based on computer simulations.

• Journal of Internet Computing and Services
• /
• v.10 no.1
• /
• pp.75-82
• /
• 2009

In this paper, we propose a robust preprocessing scheme for entropy coding in gray-level image. The issue of this paper is to reduce additional information needed when bit stream is transmitted. The proposed scheme uses the preprocessing method of co-occurrence count about gray-levels in neighboring pixels. That is, gray-levels are substituted by their ranked numbers without additional information. From the results of computer simulation, it is verified that the proposed scheme could be reduced the compression bit rate by up to 44.1%, 37.5% comparing to the entropy coding and conventional preprocessing scheme respectively. So our scheme can be successfully applied to the application areas that require of losslessness and data compaction.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.13 no.2
• /
• pp.160-170
• /
• 1988

This paper describes the outboard NIU(Network Interface Unit) using microprocessor and the hardware and software of concentrator for constructing star typed LAN(Local Area Network) based on token ring method. The NIU adapter can adapter up to four parallel and serial typed terminals. Because it has PAD function on input output data, any type of terminals can be adapted. Since the concentrator has logical switching circuit which enables data to bypass the faulted NIU adapter, this network prevents communication break. When user transmits and receives data, the concentrator constructs star typed LAN which connct both transmitting and receiving sides. A s result, this network eliminated ring latency time in other NIU exculding transmitting and receiving NIU. So the throughput of this LAN is increased. Because this LAN system consists of several modultes according to it's function, the expansion of function or the modification of method is easy.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.6 no.1
• /
• pp.49-54
• /
• 2011

In this paper, End-to-End VoIP(Voice over Internet Protocol) performance over large scale MANET(Mobile Ad-hoc Networks) is evaluated. VoIP implementation model, which can be used for large scale MANET, is suggested through this evaluation. VoIP simulator based on NS-2 network simulator is used for performance measurement. Call connection ratio as a connection performance, MOS and network delay as a transmission performance, packet loss rate as other performance is measured with this simulation. Finally, maximum $10{\sim}15km^2$ as a single MANET, 500 nodes and 100 call connections is suggested for VoIP implementation and operation conditions over large scale MANETs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.369-372
• /
• 2008

무선 센서 네트워크(WSN)는 소규모, 저비용, 저전력 지능형의 센서 노드로 구성되고, 원격 환경 감시와 군사작전 및 재난 상황 등에 응용 될 수 있는 기술이다. 이러한 센서 네트워크에서 구성된 노드의 에너지 공급은 독립된 소형배터리를 통해 이루어진다. 따라서 각 노드에서의 에너지의 효율적인 관리가 무선 센서 네트워크의 최대 쟁점이 되고 있다. 본 논문에서는 이러한 노드의 제한된 배터리 자원을 보다 효율적으로 유지 관리하기 위한 방법으로 ASIT(Advanced Sensing Interval Time) 알고리즘을 제안한다. 제안된 ASIT란 입력된 센싱 값의 변화와 센서 노드의 에너지 잔여량에 따라 센싱 주기를 제어 관리하는 방법으로 이에 대한 모델링을 수립하고, 실제 노드 관리 결과와 모델링 된 결과의 오차를 관찰하여 적중율을 향상하는 기법을 제안한 것이다. 제안된 ASIT의 알고리즘으로부터 센서 노드의 수명을 향상 시켜 궁극적으로는 무선 센서 네트워크 전체의 망 접속의 신뢰성과 노드 관리 수명을 연장시키며, 망의 토폴로지 구성의 측면에서는 전체적인 영역의 커버리지를 향상시키는 동시에 제한된 배터리 자원을 효율적으로 관리 할 수 있는 걸과를 얻게 된다.

• Journal of the Korea Society of Computer and Information
• /
• v.11 no.5 s.43
• /
• pp.1-8
• /
• 2006

Network measurement is a vital part of network traffic engineering. In a network, the metric 'capacity' characterizes the maximum throughput the path can provide when there is no traffic load, or the minimum transmission rate among all links in a path. Pathrate is one of the most widely used network capacity measurement tools nowadays. It's famous for its accurate estimation result and non restriction of the temporal network traffic condition. After several years of development, its performance becomes more stable and reliable. Extant local modes detection algorithm in pathrate is based on statistic methodology histogram. This paper suggests a new algorithm for local modes detection based on ASH (Averaged Shifted Histogram). We have implemented this algorithm and will prove it can accomplish the same task as the original one with a better result.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.8C
• /
• pp.1125-1132
• /
• 2004

In this Paper, we Propose an effective boundary matching based error detection algorithm using causal neighbor blocks to improve video quality degraded from channel error in block-coded video. The proposed algorithm first calculates boundary mismatch powers between a current block and each of its causal neighbor blocks. It then decides that a current block should be normal if all the mismatch powers are less than an adaptive threshold, which is adaptively determined using the statistics of the two adjacent blocks. In some experiments under the environment of 16bi1s burst error at bit error rates (BERs) of 10$^{-3}$ -10$^{-4}$ , it is shown that the proposed algorithm yields the improvements of maximum 20% in error detection rate and of maximum 3.5㏈ in PSNR of concealed kames, compared with Zeng's error detection algorithm.