• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.4
• /
• pp.693-697
• /
• 2005

In this paper, it was estimated the BER performance of the individual system type by applying the SFH type and the FFH type to the FH MC-DS CDMA system that combined the strong points of MC DS/CDMA and that of Frequency Mewing under the Nakagami fading channel with Multi-tone Jamming. An increase in the number of hoppings means that it can improve theBER performance by reducing the receiving burden of the FH MC DS/CDMA by achieving a frequency diversity effect. Therefore, I verified that the performances of the FH MC DS/CBMA system could be impoved by increasing the number of hoppings.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.1
• /
• pp.543-546
• /
• 2005

In this paper, it was estimated the BER performance of the individual system type by applying the SFH type and the FFH type to the FH MC-DS CDMA system that combined the strong points of MC DS/CDMA and that of Frequency Hopping under the Nakagami fading channel with Multi-tone Jamming. An increase in the number of hoppings means that it can improve the BER performance by reducing the receiving burden of the FH MC DS/CDMA by achieving a frequency diversity effect. Therefore, I verified that the performances of the FH MC DS/CDMA system could be improved by increasing the number of hoppings.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2000.05a
• /
• pp.183-187
• /
• 2000

In this paper, the performance of DS-CDMA system and FH-CDMA system has been comparision analyzed in a channel environment which is characterized by Multi-User environment and Rayleigh fading environment. The techniques of improvement of the performance has been comperision analysis evaluated when adopting MRC diversity techniques. In same condition, We are analyzed the BER(Bit Error Rate) as increase Use's number due to comparing performance of two systems by Same communication band(300KHz), jamming signal(JSR) 10∼20dB, user data-rate 300bps. In the result, the performance of DS and FH systems in multiuser and Rayleigh fading environment is improved performance when adopting MRC diversity techniques. Especially DS system has been improved performance about 9.5 times than FH system when adopting MRC diversity techniques.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2003.05b
• /
• pp.1497-1500
• /
• 2003

본 논문에서는 나카가미 페이딩 채널하에서 MC DS/CDMA 방식에 FH 방식을 적용한 FH MC/DS CDMA 시스템의 성능을 분석하였다. 나카가미 페이딩 지수 m과 MRC 다이버시티의 브랜치 수 L이 증가할 때 호핑 횟수 1과 4에 대한 분석결과 약 2.8dB의 성능차이를 보이고 있음을 앞 수 있었다. 호핑 횟수의 증가는 주파수 다이버시티 효과를 가져옴으로써 FH MC DS/CDMA 시스템에서 수신측의 부담을 줄이면서 BER 성능을 향상시킬 수 있음을 의미하며 따라서 호핑 횟수를 증가시킴으로써 부담 MC/DS CDMA 시스템의 성능을 개선할 수 있음을 입증하였다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.6 no.2
• /
• pp.141-150
• /
• 2002

In this paper, we composed orthogonal multi carrier FH/CDMA system using frequency hopping sequence. Considering hit possibilities by delayed other user's signals we searched the optimal number of user access carrier slots not to influence on performance deterioration with the variation of number of carrier slots according to the number of user access carrier slots. A]io, we evaluated the BER performance improvement due to TCM and Concatenated coding technique by computer simulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.7
• /
• pp.1118-1130
• /
• 1999

In this paper, error performance of DS/FH CDMA system has been analyzed in a radio channel which is characterized by near-far problem and multi-path fading. The DS/FH CDMA system adopts Maximum Ratio Combining(MRC) diversity and BCH(Bose-Chau dhuri-Hocquenghem) coding techniques to enhance system performance. Using the derived error probability equation, the error performance of DS/FH CDMA system has been evaluated and shown in figures to discuss as a function of PN code length(N), hopping rate(q), number of diversity branch(M), coding rate($\gamma$) and bit energy per noise power ratio ${E_b/N_o}$. The results show that DS/FH system is more effective to restrain the affection of near-far problem and multi-path fading than DS system. And there is a substantial enhancement in performance by employing an MRC diversity or BCH coding techniques. Consequently, we expected that proposed system structure is reliable to the voice communication system in near-far problem and multi-path fading channel.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.05a
• /
• pp.727-731
• /
• 2001

된 논문에서는 임펄스 잡음과 다중접속간섭(MUI) 및 나카가미 페이딩 환경으로 모델링되는 FH/CDMA 시스템을 제안하고 이의 성능을 분석하였다. 결과에 의하면 FH-CDMA 시스템은 잡음이나 페이딩의 영향보다는 여러명의 사용자가 같은 시간에 같은 주파수를 사용함으로 인한 충돌과 임펄스 잡음에 의해 더 큰 영향을 받는다. 성능 개선기법으로 다이버시티 기법과 에러정정 부호화 기법을 사용함으로써 페이딩과 다중접속 간섭에 대하여 어느 정도의 개선효과를 보이지만 임펄스 잡음의 영향으로 무선 데이터 통신을 만족하는 시스템 성능을 가질수 없었다. 따라서 한번의 재전송만을 고려한 Truncated Type-II Hybrid ARQ기법을 동시에 채용함으로써 다중접속 간섭과 임펄스 잡음에 의한 전송에러를 감소시키고 고신뢰도의 무선 데이터 통신을 만족하는 시스템 성능을 보임을 알 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.5A
• /
• pp.846-854
• /
• 2001

본 논문에서는 무선통신로 채널상에 존재하는 가우스 잡음을 포함한 협대역 A급 임펄스 잡음과 나카가미 페이딩 환경에서 하이브리드 DS/FH-CDMA MFSK 시스템의 성능을 비교 분석하고, 성능 개선 기법으로 MRC 다이버시티 수신 기법과 부호화 기법을 동시에 채용함으로써 고려되어진 시스템의 성능을 개선시켰다. 결과에 의하면 임펄스 지수가 강할수록 또한, 페이딩 지수가 작을수록 하이브리드 DS/FH-CDMA 시스템에서는 성능이 더욱 열화됨을 알 수 있었고, 성능 개선 기법으로 BCH 부호화 기법을 채용했을 경우 페이딩 지수가 증가할수록 성능개선의 폭이 큼을 알 수 있었다. 페이딩 지수가 작은 열악한 환경에서는 MRC 다이버시티 수신 기법을 채용하였을 경우 시스템 성능이 우수하였지만, 페이딩 영향이 감소할수록 BCH 부호화 기법을 채용하였을 경우 시스템 성능이 우수함을 알 수 있었다. 또한, 레일리 페이딩 환경에서 각각의 성능개선 기법을 단독으로 채용하였을 경우, 음성서비스 품질($10^{-3}$)에 도달할 수 없지만, BCH 부호화 기법과 MRC 다이버시티를 동시에 채용함으로써 강한 임펄스 잡음 하에서도 24dB 이상에서 음성서비스 기준 오율을 만족하는 성능 개선 효과를 얻을 수 있었고, 페이딩 지수가( $m_{i}$=3) 이상에서는 강한 임펄스 잡음이 부가되어도 21dB에서 $10^{-3}$을 만족하고 28dB 이상에서는 데이터 서비스 기준($10^{-5}$) 오율을 만족하는 우수한 성능 개선 효과를 보임으로써 다이버시티 가지수와 부호화의 이득에 의한 에러 성능이 향상되었다.

• Journal of Advanced Navigation Technology
• /
• v.5 no.1
• /
• pp.11-18
• /
• 2001

In this paper, we evaluated the performance of Orthogonal MC/FH-CDMA system considering the hit of frequency hopping patterns, and obtained the degree of the performance improvement by adopting TCM scheme under frequency selective Rayleigh fading channel. From the performance analysis, it is known that the error performance is improved, since delay time relative to symbol time is reduced as the number of carrier is increased. On the other hand, it is found that BER performance is improved about $5{\times}10^{-2}$ degree by adopting TCM scheme, and higher S/N is required if the QoS of voice (BER = $10^{-3}$) must be achieved.

• The KIPS Transactions:PartC
• /
• v.12C no.2 s.98
• /
• pp.223-228
• /
• 2005

The existing mobile communication system called DS/CDMA system, which is serviced widely nowadays, has some problems such as the severe ISI and multiple access interferences under the multi-path fading channel when applied to high-speed data transmission like multimedia transmission. To compensate these problems, we propose a sub-code multi-code hybrid DS/FH (Frequency Hopping) SS (Spread Spectrum) System by combining the multi-code system that restrains the multiple access interference with the hybrid DS/FH SS technique that reduces ISI(Intersymbol Interference) effect for high-speed transmission. Moreover, we implement and propose the sub-code technique to remedy the problems of the generic multi-code system. To verify the performance of the proposed system, the computer simulations are executed under the various channel environments.