http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
OFDM 통신 시스템에서 비선형 증폭기 특성을 고려한 전력 효율과 대역 효율
이재은,유흥균 충북대학교 컴퓨터정보통신 연구소 2003 컴퓨터정보통신연구 Vol.11 No.2
OFDM 시스템뿐만 아니라 모든 통신 시스템에서는 HPA(high power amplifier)의 비선형 특성을 고려하는 것이 중요하다. 본 논문에서는 OFDM 통신 시스템에서 전력 효율과 대역효율을 동시에 고려한 새로운 성능 평가지수(D)를 분석한다. IBO(input backoff)의 크기와 부반송파 수에 따라 다른 값을 갖는 비선형 왜곡 잡음 성분(N_(d))을 고려하며, 대역폭의 변화에 따른 대역 효율을 사용하여 성능 지수를 구함으로써 IBO에 대해 서로 상반관계(tradeoff)에 있는 전력 효율과 대역 효율의 특성을 분석하였다. It is very important to consider the nonlinear effects of the HPA(high power amplifier) not only in the OFDM communication systems but in the other digital communication systems. In this paper, we investigate a new performance figure-of-merit (D) that reflects the power efficiency and spectrum efficiency at the same time. The performance figure-of-merit is expressed to include both the spectrum efficiency and the power efficiency. E_(b)/(N_(o)+N_(d)) including the nonlinear distortion value (N_(d)) and the spectral efficiency depend on the magnitude of IBO(input backoff) and the number of subcarriers. Therefore, we analyze the variation characteristics of the power efficiency and spectrum efficiency which has the tradeoff relationship.
Optimum chip waveform shaping and performance analyses in spectrum-overlapped DS-CDMA system
Ryu, Heung-Gyoon 충북대학교 컴퓨터정보통신 연구소 2004 컴퓨터정보통신연구 Vol.11 No.3
The effects of chip waveform shaping on the interference suppression capability are studied in a spectrum-overlapped DS-CDMA system with coherent Rake receiver under Rayleigh multipath fading channel. Time-limited sinc function(TLSF) with a time-domain roll-off factor is proposed as an optimum chip waveform in a spectrum-overlapped DS-CDMA system that can minimize ACI as well as MAI and SI. The roll-off factor is controlled to minimize the interferences for the spectrum overlapping ratio. TLSF with optimum roll-off factor is presented and several numerical results are shown to verify the performance improvements over the conventional chip waveforms. Two bandwidth efficiency factors are defined. The capacity and throughput performances are numerically obtained in a specific overlapping ratio. It is found that TLSF with roll-off factors of 1 and 8 are determined as an optimum chip waveform when the time-bandwidth products are 1.2 and infinite. respectively. Performance is compared between the proposed optimum chip waveforms and the conventional waveforms in terms of capacity and throughput. It is shown that the proposed waveforms can provide more capacity and throughput than the conventional waveforms as the amount of spectrum overlap is increased. Therefore, it is concluded that the TLSF is appropriate for the spectrum-overlapped cellular environment.
Orthogonal tranmission of SFBC-OFDM for reducing the ICI caused by phase noise
Ryu, Heung-Gyoon,Li, Ying-Shan 충북대학교 컴퓨터정보통신 연구소 2006 컴퓨터정보통신연구 Vol.14 No.1
In the (orthogonal frequency division multiplexing) OFDM system, (inter-subcarrier-interference) ICI caused by phase noise or frequency offset breaks down the orthogonality between subcarriers so that degrades system performance. In this paper, an orthogonal transmission of (space-frequency block coding OFDM) SFBC OFDM which combines SFBC and (orthogonal transmit diversity) OTD is proposed to reduce ICI effectively and compared with other phase noise compensation methods. (common phase error) CPE and ICI are analyzed by the phase noise linear approximation method in the 4 kinds of systems. (carrier-to-interference ratio) CIR, (peak to average power ratio) PAPR, (peak interference to carrier ratio) PICR, (bit error rate) BER and bandwidth efficiency are discussed to analyze the system performance affected by phase noise or frequency offset. By assigning orthogonal code to each of antenna, the (self-channel interference) SCI that usually happens in the SFBC method can be easily avoided in this new SFBC method. The proposed orthogonal transmission of SFBC method considerably reduces ICI and SCI. In conclusion, the proposed SFBC method using diversity technique shows excellent performance without the loss of bandwidth efficiency, compared with the other conventional methods.
Ryu, Heung-Gyoon 충북대학교 컴퓨터정보통신 연구소 2006 컴퓨터정보통신연구 Vol.14 No.2
Error probability analysis is found for the frequency-hopped noncoherent M-ary frequency shift keyed(FH-MFSK) system using the jammer state information(JSI) against combined tone and noise jammers. It is considered that a portion of a given total jamming power used by noise jamming is ε, a fractional ratio of tone jamming is ρ, and the symbol energy-to-noise jamming power spectral density ratio is E_(s)/J_(O). Furthermore, the channel is assumed to be a Rayleigh fading channel, and both signaling tones and combined jamming are also assumed to be affected by fading environment independently. System performance is evaluated in terms of the Chernoffbound(D) on the probability of symbol error. In Rayleigh fading channel with E_(s)/J_(O)=10 [dB], ρ=0.2 and ε=0.3 conditions, the difference value of D parameters between the system with JSI and one with no JSI is about 0.2. And, the system with JSI has more effect on overall system performance than one without JSI, regardless of the portion variation of the noise jamming power. In E_(s)/J_(O)=10[dB], system performance with-out JSI is the poorest when the tone jamming ratio is 0.1 regardless of the portion of noise jamming power, compared to system with JSI. Thus, the proper combination of noise and tone jamming is used to get better performance.
A Complexity Reduction Scheme for SLM-based OFDM Communication System
Heung-Gyoon Ryu,Garik Markarian 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
SLM (selective mapping) method is one of the efficient techniques to reduce PAPR in OFDM(orthogonal frequency division multiplexing) system. In this paper, we propose a new SLM method which rotates the phase of input data after IFFT by using Walsh Hadamard code to solve this problem. From the simulation results, we can find that the proposed SLM method has 0.5 dB lower PAPR reduction effect than common SLM in same number of copy branch U. However, it can reduce a computational burden more than about 50%.