KR20040027566A - A method for the analysis of phase noise in OFDM communication systems - Google Patents
A method for the analysis of phase noise in OFDM communication systems Download PDFInfo
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Abstract
Description
고속의 데이터가 무선 채널로 전송될 경우 전파는 전송 도중 다중 경로 페이딩과 도플러 페이딩 현상이 나타나게 되어 시스템의 성능이 저하되게 된다. 이로 인해 고속 멀티미디어 데이터 전송을 위해 제시되고 있는 방식이 다중 반송파 전송방식이며 이중 직교 주파수 분할 다중 반송파 전송방식은(OFDM : Orthogonal Frequency Division Multiplexing) 상호 직교성이 있는 부반송파를 사용함으로써 스펙트럼 효율이 다른 다중 반송파 전송 방식에 비해 우수하다는 장점을 가진다.When high-speed data is transmitted over a wireless channel, radio waves may cause multipath fading and Doppler fading during transmission, thereby degrading system performance. For this reason, a multi-carrier transmission scheme is proposed for high-speed multimedia data transmission, and a dual orthogonal frequency division multiplexing (OFDM) method uses multi-carrier transmission with different spectral efficiencies by using subcarriers with mutual orthogonality. It has the advantage of being superior to the method.
그러나 OFDM방식은 여러 개의 부반송파를 사용하기 때문에 송신단과 수신단의 반송파 주파수가 일치되지 못하면 부반송파 사이의 직교성이 파괴되어 부반송파들 사이에 인접 채널 간섭이 발생한다. 따라서 본 특허에서는 위상잡음에 따른 OFDM통신 시스템의 성능 분석을 수행할 수 있는 기법을 개발하였다.However, because the OFDM method uses multiple subcarriers, if the carrier frequencies of the transmitter and the receiver do not match, the orthogonality between the subcarriers is broken and adjacent channel interference occurs between the subcarriers. Therefore, the present patent has developed a technique for performing the performance analysis of the OFDM communication system according to the phase noise.
OFDM 통신 시스템에서의 성능분석 및 예측을 위한 위상잡음 영향 분석 기법을 개발함으로서 고속 무선데이터 전송 기술을 확보하고자 한다.The purpose of this study is to secure a high-speed wireless data transmission technology by developing a phase noise effect analysis method for performance analysis and prediction in OFDM communication systems.
도1은 간략화한 전송모델1 is a simplified transmission model
도 2는 phase noise power에 따른 CPE , ICI power2 shows CPE and ICI power according to phase noise power.
도 3은 phase noise power에 따른 SIR , effective SNR3 shows SIR and effective SNR according to phase noise power.
도 4는 phase noise spread에 따른 CPE , ICI power4 shows CPE and ICI power according to phase noise spread.
도 5는 phase noise spread에 따른 SIR , effective SNR5 shows SIR and effective SNR according to phase noise spread.
일반적인 오실레이터의 출력신호는 phase noise에 의해 위상이 랜덤하게 흔들리는 현상이 발생된다. 이로 인한 영향은 두가지로 나눌 수 있는데 common phase error와 ICI이다. 신호가 무선채널로 송신되어 채널의 임펄스 응답 h(t)와 오실레이터의 phase noise Ø(t)에 의해 영향을 받은 수신단의 신호는 다음과 같이 쓸 수 있다.In general, the oscillator output signal is randomly shaken by phase noise. The effects can be divided into two categories: common phase error and ICI. The signal of the receiver is affected by the impulse response h (t) of the channel and the phase noise Ø ( t ) of the oscillator can be written as follows.
계산을 보다 간단하게 하기 위해 Ø(n)이 매우 작은 값을 갖는다고 가정하면 다음과 같이 나타낼 수 있다.To make the calculation simpler, assuming that Ø ( n ) has a very small value, we can write
그러므로 수신단에서 OFDM 복조된 신호는 다음과 같이 세 부분으로 나누어정리 할 수 있다.Therefore, the OFDM demodulated signal can be divided into three parts as follows.
위 식에서 첫 번째 부분이 원하는 신호부분, 두 번째 부분은 phase noise Ø(n)에 의해 생기는 부반송파 간섭부분 그리고 세 번째 부분은 백색잡음을 나타낸다. 위 식의 반송파 간섭부분에서k=i인 경우를 정리하면 다음과 같이 나타낼 수 있다.In the above equation, the first part is the desired signal part, the second part is subcarrier interference caused by phase noise Ø ( n ), and the third part is white noise. If k = i in the carrier interference portion of the above equation can be summarized as follows.
즉,P i 는 i 번째 반송파에 작용하는 phase noise의 영향을 나타내며 그 크기는 수신신호에 비례한다. 그러므로 위 식은 모든 반송파에 공통적으로 작용하는 common phase error를 나타낸다. 다음으로k≠i인 경우에는 다음과 같이 정리 된다.That is, P i represents the effect of phase noise on the i th carrier and its magnitude is proportional to the received signal. Therefore, the above equation represents a common phase error common to all carriers. Next, if k ≠ i , it is summarized as follows.
위 식에서A i 는 (N-1)개의 , 주파수 이동된 Ø(n)의 합과 수신신호와의 곱으로 이루어져 있으므로 마치 잡음과 비슷한 성격의 i번째 부반송파에 작용하는 다른부반송파의 간섭을 나타낸다. 이제 보다 간편하게 common phase error와 반송파 간섭을 계산하기 위해서 n번째 부반송파를 제외한 나머지 반송파들을 0으로 설정하고 n번째 부반송파의 심볼 크기는X k =1로 가정하면 전송모델을 다음과 같이 매우 간략한 그림으로 나타낼 수 있다. 도 1에서k≠i인 경우In the above equation, A i consists of (N-1), the sum of the frequency shifted Ø ( n ) and the product of the received signal, indicating interference of other subcarriers acting on the i-th subcarrier, which is similar to noise. Now, to make it easier to calculate common phase error and carrier interference, assume that the remaining carriers except the nth subcarrier are set to 0 and the symbol size of the nth subcarrier is X k = 1 Can be. In the case of k ≠ i in Figure 1
가 된다. 즉, i 번째 부반송파에 작용하는 k 번째 부반송파 간섭을 나타내는데 부반송파 간섭은 주파수 천이된 페이즈 노이즈 프로세스를, T시간동안 크기 1/T인 rect 펄스 형태의 임펄스 응답을 갖는 필터에 인가한 출력형태를 갖는다. 그러므로 부반송파 간섭의 PSD는 다음과 같이 나타낼 수 있다.Becomes That is, it represents k-th subcarrier interference acting on the i-th subcarrier. The subcarrier interference has an output form in which a frequency shifted phase noise process is applied to a filter having an impulse response in the form of a rect pulse of size 1 / T for a T time. Therefore, the PSD of the subcarrier interference can be expressed as follows.
그러므로 i번째 부반송파에 대한 k번째 부반송파 간섭의 평균전력은 다음과 같이 계산 할 수 있다.Therefore, the average power of the k-th subcarrier interference for the i-th subcarrier can be calculated as follows.
다음으로 CPE를 계산하기 위해서 도 1에서k=i인 경우를 보면가 되므로 CPE의 PSD는 다음과 같이 나타낼 수 있다.Next, in the case of k = i in Figure 1 to calculate the CPE Since the PSD of the CPE can be expressed as follows.
따라서 CPE의 평균전력은 다음과 같이 표현되며 페이즈노이즈 특성이 OFDM심볼기간동안 stationary 하다면 CPE는 모든 부반송파에 공통적인 크기로 작용하게된다.Therefore, the average power of the CPE is expressed as follows. If the phase noise characteristic is stationary during the OFDM symbol period, the CPE acts as a common size for all subcarriers.
본 논문에서는 페이즈 노이즈에 의한 영향을 분석하기 위해서 다음과 같이 페이즈 노이즈 모델을 가정하였다.In this paper, we assume a phase noise model as follows to analyze the effect of phase noise.
위 식에서 parameter a는 중심주파수로부터 ±f l 까지의 phase noise level을, parameter b는f l ∼f h 까지의 주파수가 증가함에 따른 노이즈 감쇄의 가파름을, parameter c는 white phase noise 층을 결정한다.In the above equation, parameter a determines the phase noise level from ± f l from the center frequency, parameter b determines the steepness of noise attenuation as the frequencies increase from f l to f h , and parameter c determines the white phase noise layer.
1. phase noise power에 따른 영향1. Effect of phase noise power
먼저 오실레이터 phase noise power에 따른 영향을 계산하기 위하여 phase noise PSD의 메인대역폭은 일정하게 고정시키고 power가 증가함에 따른 영향을 계산하여 도 3, 도 4에 나타내었다. 도 2에는 phase noise PSD의 메인대역폭은 고정시킨후 phase noise power에 따른 CPE와 ICI power를 나타내었다. 이때 phase noise PSD의 메인대역폭이 부반송파 대역폭내에 존재하기 때문에 CPE는 phase noise power의 증가에 따라 비례해서 증가하나 ICI power는 거의 변화가 나타나지 않는 것을 알 수 있다.First, in order to calculate the influence of the oscillator phase noise power, the main bandwidth of the phase noise PSD is fixed and the effects of increasing the power are shown in FIGS. 3 and 4. 2 shows the CPE and ICI power according to the phase noise power after fixing the main bandwidth of the phase noise PSD. At this time, since the main bandwidth of the phase noise PSD is within the subcarrier bandwidth, the CPE increases proportionally with the increase of the phase noise power, but the ICI power hardly changes.
도 4에는 phase noise power에 따른 SIR과 effective SNR을 나타내었다.phase noise power가 증가함에 따라 SIR과 effective SNR이 급격하게 떨어지며 phase noise power 가 0.03을 넘어서게 되면 SIR과 effective SNR곡선이 거의 같게 나타나는데 이는 무선채널의 부가성 백색잡음의 영향보다 phase noise 의 영향이 우세해지는 것을 의미한다.4 shows the SIR and the effective SNR according to the phase noise power. As the phase noise power increases, the SIR and the effective SNR drop sharply, and when the phase noise power exceeds 0.03, the SIR and the effective SNR curves are almost the same. This means that the influence of phase noise is superior to that of additional white noise in the channel.
2. phase noise spread에 따른 영향2. Effect of phase noise spread
두 번째로 phase noise spread에 따른 영향을 분석하기 위하여 phase noise power는 일정하게 유지한 상태에서 PSD의 메인대역폭을 증감시키며 그 영향을 계산하였다. 도 6에서 phase noise PSD의 메인대역폭이 증가함에 따라 크지는 않으나 CPE는 감소하고 ICI는 증가함을 알수 있다. 그러나 결과적으로 CPE의 감소량과 ICI의 증가량이 거의 비슷하여 도 7의 SIR과 effective SNR은 phase noise spread에는 거의 관계없이 일정하게 나타나는 것을 확인할 수 있다.Second, to analyze the effect of phase noise spread, we calculated the effect by increasing and decreasing the main bandwidth of PSD while keeping the phase noise power constant. As shown in FIG. 6, as the main bandwidth of the phase noise PSD increases, the CPE decreases and the ICI increases. However, as a result, the decrease in CPE and the increase in ICI are almost the same, and thus, the SIR and the effective SNR of FIG. 7 can be seen to be constant regardless of the phase noise spread.
본 특허에서는 고속 무선 LAN OFDM 시스템의 무선채널에서의 성능을 분석하기 위해 다양한 채널모델에 따른 오실레이터 페이즈 노이즈에 의한 영향을 SIR과 이 SIR을 고려한 effective SNR을 효율적으로 구하는 기법을 개발하였다. 오실레이터 페이즈 노이즈에 의한 영향을 계산하기 위하여 페이즈 노이즈 모델을 설정하고 페이즈 노이즈 평균전력과 메인대역폭을 증감시키면서 그 영향을 분석하였다. 페이즈 노이즈의 평균전력이 증가할수록 SIR 과 effective SNR이 급격하게 떨어지며r=30dB인 경우 phase noise power가 0.03을 넘어서게 되면 무선채널의 부가성 백색잡음의 영향보다 phase noise의 영향이 더 우세해져 SIR과 effective SNR 곡선이같게 나타났다. 또한 phase noise PSD의 메인대역폭을 극단적으로 부반송파의 대역폭의 약 2배까지 증가시키면서 영향을 분석하였는데 결과적으로 CPE의 감소량과 ICI의 증가량이 거의 비슷하여 SIR 과 effective SNR이 거의 일정하게 나타났다. 즉, 오실레이터 패이즈 노이즈 PSD의 메인대역폭의 변화에 따른 영향의 차이는 매우 미미하다고 볼 수 있으며 단 phase noise power가 증가함에 따라 성능의 열화정도를 쉽게 예측할 수 있다.In this patent, we have developed a technique to efficiently calculate the effect of oscillator phase noise according to various channel models and the effective SNR considering the SIR to analyze the performance of the high-speed wireless LAN OFDM system. To calculate the effects of oscillator phase noise, we set up a phase noise model and analyze the effects of increasing and decreasing phase noise average power and main bandwidth. As the average power of phase noise increases, the SIR and effective SNR drop sharply, and when r = 30 dB , if the phase noise power exceeds 0.03, the effect of phase noise is more prevalent than that of the additional white noise of the radio channel. The effective SNR curve is the same. In addition, we analyzed the effects of increasing the main bandwidth of the phase noise PSD to about twice the bandwidth of the subcarrier. As a result, the decrease of CPE and the increase of ICI were almost the same, resulting in almost constant SIR and effective SNR. In other words, the difference of the influence of the oscillator phase noise PSD due to the change of the main bandwidth can be considered very small, and as the phase noise power increases, the degree of performance degradation can be easily estimated.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR100557875B1 (en) * | 2003-08-21 | 2006-03-10 | 주식회사 애드텍 | Method for preparing of pressure sensitive adhesive tape for dicing comprising pvc support and adhesive tape |
| KR100651556B1 (en) * | 2004-06-30 | 2006-11-29 | 삼성전자주식회사 | Apparatus and method for estimating carrier to interference and noise ratio in communication system |
| KR100768327B1 (en) * | 2006-05-23 | 2007-10-17 | 인하대학교 산학협력단 | Apparatus and method for estimating carrier to interference and noise ratio in systems using multi-carrier signal |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| KR100557875B1 (en) * | 2003-08-21 | 2006-03-10 | 주식회사 애드텍 | Method for preparing of pressure sensitive adhesive tape for dicing comprising pvc support and adhesive tape |
| KR100651556B1 (en) * | 2004-06-30 | 2006-11-29 | 삼성전자주식회사 | Apparatus and method for estimating carrier to interference and noise ratio in communication system |
| KR100768327B1 (en) * | 2006-05-23 | 2007-10-17 | 인하대학교 산학협력단 | Apparatus and method for estimating carrier to interference and noise ratio in systems using multi-carrier signal |
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