• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.6A
• /
• pp.438-449
• /
• 2012

This paper presents new CRC-p codes for VHF band maritime wireless communication system based on performance analysis of various CRC codes. For this purpose, we firstly describe the method of determination of undetected error probability and minimum Hamming distance according to variation of CRC codeword length. By using the fact that the dual code of cyclic Hamming code and primitive BCH code become maximum length codes, we present an algorithm for computation of undetected error probability and minimum Hamming distance where the concept of simple hardware that is consisted of linear feedback shift register is utilized to compute the weight distribution of CRC codes. We also present construction of transmit data frame of VHF band maritime wireless communication system and specification of major communication parameters. Finally, new optimal CRC-p codes are presented based on the simulation results of undetected error probability and minimum Hamming distance using the various generator polynomials of CRC codes, and their performances are evaluated with simulation results of bit error rate based on the Rician maritime channel model and ${\pi}$/4-DQPSK modulator.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1993.06a
• /
• pp.276-279
• /
• 1993

이 논문에서는 페이딩이 있는 채널에서 충격성 잡음이 있을 때 부호 상관 수신기를 쓰는 DS/SSMA 시스템의 성능을 분석하였다. 좀 더 자세히 말하면, 확산 수열이 짧을 때에는 직접 계산으로, 확산 수열이 길 때에는 근사식으로 부호 상관 수신기를 쓰는 DS/SSMA 시스템의 비트 오류 발생 확률을 얻었다. 이를 통해 사용자가 한 사람일때에는 이 시스템의 성능이 신호대 잡음비의 변화에 크게 영향을 받지 않는다는 것을 보였다.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2003.11a
• /
• pp.441-444
• /
• 2003

본 논문에서는 CDMA S-ALOHA 시스템에서 단말기들의 공평한 패킷 전송을 보장하기 위한 중앙 집중형 백오프 기법을 제안하고 이에 대한 성능을 분석한다. 전용 코드 방식의 CDMA 시스템에서는 각 단말기들이 고유의 확산코드를 이용하여 패킷을 전송하므로 패킷 충돌로 인한 전송 실패는 없는 반면, 다원 전속 간섭에 의한 비트 오류가 패킷 전송의 실패 요인이 된다. 제안한 기법에서는 기지국이 망의 부하에 따라 단말기들의 백오프를 위한 확률을 계산하여 방송하고, 단말기에서는 이를 기반으로 패킷 전송을 시도한다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.13 no.6
• /
• pp.453-460
• /
• 1988

The error probability for coherent frequency-hopped spread-spectrum multiple-access communications is computed by using characteristic function method. We employ PSK as a modulation scheme. The channel capacity is performance measure and the minimum bit signal-to-noise ratio for reliable communications is obtained.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 2004.11a
• /
• pp.357-357
• /
• 2004

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.8A
• /
• pp.1126-1132
• /
• 1999

In this paper, we consider the superposed 16-QAM CDMA system for subband coded (SBC) image transmissions. We divide the SBC image bit into two group according to its significance. First, we investigate the average bit error rate (BER) of the overall system when the significance of bits is ignored. Next, we investigate the optimal signal constellation and processing gain that maximizes the peak signal-to-noise ratio (PSNR) of SBC image, subject to a fixed power and bandwidth constraint. We examine the performance improvement over the conventional equal distane, equal processing gain system, and the equal error protection (EEP) system.

• The Journal of the Korea Contents Association
• /
• v.7 no.12
• /
• pp.303-310
• /
• 2007

Compressed video bitstreams are intended for real-time transmission over communication networks. Because video compression algorithms eliminate the temporal, spatial, and statistical redundancies, the coded video bitstreams are very sensitive to transmission errors. We propose an error resilient video coding technique to limit the effect of error propagation in low bit-rate video coding. The success of error resilient coding techniques relies on how accurately the transmission errors can be detected. To detect the transmission error, we propose a very simple error detection technique based on data hiding Next, we conceal the corrupted MB data using intra MB refresh and motion compensation with the estimated motion vector and compare the simulation results. This method will be useful in video communication in error Prone environment such as WCDMA networks.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.11A
• /
• pp.1820-1826
• /
• 2001

In this paper, we present a modeling scheme for the already-installed two-wire home phone lines with arbitrary topologies and show that the inter-symbol interference due to the topology can be removed using an adaptive equalizer. The transmission characteristics of the arbitrary-configured two-wire home phone lines can be analyzed through the ABCD matrices. The simulation result shows that the impedance mismatch due to the branch lines renders nulls in the frequency response or delayed pulses in the impulse response. These nulls or delayed pulses cause inter-symbol interference that inhibits correct signal detection. An adaptive equalizer is shown to be effective in eliminating the interference. Also, the simulation result shows that the equalizer converges in 1.5 ms at a data rate of 1 Msps at signal-to-noise ratios greater than 15 dB. In addition, from the result of relation between E$\_$b//N$\_$and BER(Bit Error Rate), we can see that E$\_$b//N$\_$o/ more than 19 dB is required for the data communication with a BER less than 10$\^$-5/.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.1A
• /
• pp.34-42
• /
• 2000

In this paper, the closed form expression for the average bit error probability(BER) is derived for diversity reception using an L-branch maximal ratio combining(MRC) system which has same fading index and different fading index. Also, the BER to have same average power and Nakagami m-distribution for a generalized selection combining(SC) is derived, whereby the signal with the largest amplitude is selected from the original diversity branches in the channel, the order statistics is applied. Especially, when L is 1 in a selective diversity, the derived expression leads to that of DPSK in which SC is not applied in Nakagami fading. Changing the diversity branch L and fading index m, we compare the performance of MRC and SC.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.4 s.346
• /
• pp.39-43
• /
• 2006

In this contribution, the achievable performance of orthogonal multicarrier DS-CDMA systems employing synchronous uplink transmissions is investigated. The bit error ratio (BER) performance is analyzed under dispersive Rayleigh multipath fading conditions as a function of the number of users.