• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.4 no.3
• /
• pp.653-660
• /
• 2000

In this paper, an adaptive interference excision scheme with multiple adaptive filter bank using an adaptive algorithm is proposed. This scheme suppresses interference in the wavelet packet transform domain for the direct spread spectrum communication systems. Using the Monte-Carlo simulation, we analyze the performance of the direct spread spectrum communication systems with this excision scheme using LMS and RLS adaptive algorithms in AWGN and interference channel.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.5C
• /
• pp.439-444
• /
• 2010

In this paper, we derive and analyze the channel capacity of the spread spectrum watermarking (SSW) system as an information-theoretic point of view in closed-form approximation formula in order to analyze the effect of the wireless multipath/shadowing channel. It is important to analyze the channel capacity to transmit an additive data through existing wireless channel by the SSW system. From the results, we confirm that the channel capacity of the SSW system can be determined by the HWR, WNR, PN length and host sampling frequency. Also, we verified that the variation of the channel capacity when the SSW system applied to Nakagami-m fading and Log-normal shadowing channel. The results of this paper can be applied to general spread spectrum watermarking system.

• Proceedings of the KAIS Fall Conference
• /
• 2003.06a
• /
• pp.250-252
• /
• 2003

본 논문에서는 콘벌루션 부호를 사용한 대역확산 방식의 디지틀 통신모뎀을 FPGA를 이용하여 설계 및 검증을 하였다. 대역확산 방식에서의 콘벌루tus부호기(K=3, R=1/2), PN code(128chip) generator와 비터비 디코더를 Xilinx사의 FPGA 디자인 툴인 Xilinx Foundations3.1을 사용하여 VHDL simulation과 timing simulation을 수행하였고, FPGA 회로설계 검증 장비인 EDA-Lab 3000 장비를 사용하여 Xilinx사의 SPARTAN2 2S100PQ208칩에 configuration 한 후 Agilent사의 1681A logic analyzer를 사용하여 설계된 회로의 동작을 검증하였다.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.5 no.1
• /
• pp.24-36
• /
• 2002

It is important to use frequency resource effectively to support much more users, to maximize the DS-CDMA system performance. In this paper, we use MPSK, QAM, MFSK and PR coder as a baseband modulation method for DS-CDMA system. Increasing user's number, we compare the performance of each system using different baseband modulation method, by expecting BER performance. BPSK has generally good performance, in case of low power operation of terminal 8FSK has excellent performance relatively, PR has excellent performance when high power operation of terminal and also good for situation of excessive user's number. QAM is not suitable for DS-CDMA system.

• Aerospace Engineering and Technology
• /
• v.10 no.1
• /
• pp.45-53
• /
• 2011

This paper is technical review about Direct Sequence Spread Spectrum(DSSS) to apply in launch vehicle system. First, we introduce communication protocol(carrier frequency, code length, process gain, data rate, chip rate etc) about several application system using DSSS. And then, we survey and summarize the effect of doppler shift to the DSSS. The doppler shift is important error factor for PN code tracking in the fast moving system like launch vehicle. So, spread spectrum code acquisition technique for a direct sequence system in the presence of doppler effect must be investigated.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.8
• /
• pp.1629-1637
• /
• 2003

In this paper, we analyzed the performance of a hybird DS/SFH(Direct­Sequency­Slow Frequency­Hopping) Spread Spectrum system with BFSK modulation over Nakagami­m fading channel with multitone jamming. The performance of the system was improved when a frequency bowing rate increased. In case that process gain of hybrid DS/SFH Spread Spectrum system to be fixed, the hybrid DS/SFH Spread Spectrum takes the low bit error probability than a DS Spread Spectrum system. Also, when the fading index m increases, the fading effect decrease, when the JSR(jamming to signal power ratio) increases ,the performance of a hybrid DS/SFH Spread Spectrum system improved than DS Spread Spectrum system. The result, we have been proved that performance of a hybrid DS/SFH Spread Spectrum was superior to DS Spend Spectrum system over Nakagami­m fading with tome jamming.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.15 no.6
• /
• pp.494-505
• /
• 1990

This paper reports on the development of a DPSK demodulator of DS spread spectrum communications that use one SAW convolver. The spreading code chip pattern is changed from bit to bit in data portion of packet. And code chip is PSK modulated. Compared with simulation, experiment shows that the DPSK signal spreaded can be demodulated by using only one SAW convolver. And the theoretical performance of this DPSK demudulator is equal to CSK demodulator wich uses two SAW convolvers.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1993.10a
• /
• pp.687-690
• /
• 1993

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1991.10a
• /
• pp.326-330
• /
• 1991

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.4 no.3
• /
• pp.517-526
• /
• 2000

In this paper, we propose the trellis coded spread spectrum communication system with one channel signal selection of the subset by the PN code. This paper proposes the Viterbi decoder that have the squared Euclidean distance of the order phase difference as well as 1st order phase difference as the branch metrics by using the multiple symbol detection method. TCM method was developed to overcome limited power and bandwidth efficiently in digital communication. we multiply one of convolution code's output data to PN code for applying TCM to the spread spectrum. We investigated the performance of the direct sequence/spread spectrum communication system with trellis coded modulation. In this system, we could improved the coding gain in the spread spectrum.