本發明涉及無線通訊領域，尤其涉及一種多載波干擾消除電路及使用其的訊號收發系統。The present invention relates to the field of wireless communications, and in particular, to a multi-carrier interference cancellation circuit and a signal transceiving system using the same.
在無線收發系統中，當訊號發送電路經由通訊通道傳送訊號至訊號接收電路時，訊號接收電路必須知道訊號的起始與結束，才能正確解調訊號。但是通訊通道產生的延遲效應，以及訊號發送電路與訊號接收電路的振盪器頻率不匹配，都會產生多載波頻率偏移的現象，這將加大訊號解調的難度，進而造成通訊系統的錯誤率大增。其中尤以頻率偏移所造成的多載波間干擾對通訊系統效能影響最為嚴重。In the wireless transceiver system, when the signal transmitting circuit transmits the signal to the signal receiving circuit via the communication channel, the signal receiving circuit must know the start and end of the signal to correctly demodulate the signal. However, the delay effect generated by the communication channel and the mismatch between the signal transmission circuit and the oscillator frequency of the signal receiving circuit may cause multi-carrier frequency offset, which will increase the difficulty of signal demodulation and cause the error rate of the communication system. Great increase. Among them, the multi-carrier interference caused by the frequency offset has the most serious impact on the performance of the communication system.
目前，隨著多媒體日益發展，無線網路需要傳輸的訊號已經不再是單純的語音或文字，而更多的是具聲光效果的圖文資訊，例如行動電話的語音影像傳輸，無線區域網(Wireless Local Area Network，WLAN)的高速資料傳輸等服務專案，這都必須依靠高速傳輸速率才可以達成。因此，作為無線高速傳輸的主流技術正交頻分複用(Orthogonal Frequency Division Multiplexing，OFDM)技術扮演的角色愈趨重要，而克服OFDM系統收發端之間的頻率偏移所造成的多載波間干擾效應更是需要一個快速且精確的多載波頻率估測裝置來改善系統效能。然而，實際情況下，此類多載波頻率估測裝置接收到的多載波訊號往往會受到其他系統的強訊號干擾，若不先行消除該干擾訊號，就會導致後續多載波頻率估測的精確度受到影響，使得OFDM系統效能得不到應有的提升。At present, with the development of multimedia, the signal that the wireless network needs to transmit is no longer pure voice or text, but more of the audio-visual image information, such as voice image transmission of mobile phones, wireless area network. (Wireless Local Area Network, WLAN) service projects such as high-speed data transmission, which must be achieved by relying on high-speed transmission rates. Therefore, as the mainstream technology of wireless high-speed transmission, the role of Orthogonal Frequency Division Multiplexing (OFDM) technology becomes more and more important, and overcomes the inter-carrier interference caused by the frequency offset between the transceiver terminals of the OFDM system. The effect requires a fast and accurateMulti-carrier frequency estimation devices to improve system performance. However, in actual situations, the multi-carrier signals received by such multi-carrier frequency estimation devices are often interfered by strong signals from other systems. If the interference signals are not eliminated first, the accuracy of subsequent multi-carrier frequency estimation will be caused. Affected, the OFDM system performance is not improved.
有鑒於此，需提供一種多載波干擾消除電路，能消除多載波訊號中的干擾訊號，以利於進行多載波頻率偏移估測。In view of this, it is necessary to provide a multi-carrier interference cancellation circuit, which can eliminate interference signals in multi-carrier signals, thereby facilitating multi-carrier frequency offset estimation.
此外，還需提供一種訊號收發系統，能消除多載波訊號中的干擾訊號，以利於進行多載波頻率偏移估測。In addition, a signal transceiving system is needed to eliminate interfering signals in multi-carrier signals to facilitate multi-carrier frequency offset estimation.
本發明一實施方式所提供的多載波干擾消除電路，用於消除多載波訊號中的干擾訊號，其中多載波訊號包括第一訓練序列。多載波干擾消除電路包括訓練序列產生電路、第一乘法器、第二乘法器、移相電路、緩衝器及加法電路。訓練序列產生電路用於產生第二訓練序列，第二訓練序列與第一訓練序列正交。第一乘法器用於將多載波訊號附上第二訓練序列，以得到新多載波訊號。第二乘法器用於將第一乘法器輸出的新多載波訊號附上第二訓練序列，以得到干擾訊號。移相電路用於轉換第二乘法器輸出的干擾訊號的相位，以獲得干擾訊號的相反數。緩衝器用於緩存多載波訊號。加法電路用於將緩衝器所緩存的多載波訊號附上干擾訊號的相反數，以消除干擾訊號。A multi-carrier interference cancellation circuit according to an embodiment of the present invention is configured to cancel an interference signal in a multi-carrier signal, where the multi-carrier signal includes a first training sequence. The multicarrier interference cancellation circuit includes a training sequence generation circuit, a first multiplier, a second multiplier, a phase shifting circuit, a buffer, and an adding circuit. The training sequence generation circuit is operative to generate a second training sequence that is orthogonal to the first training sequence. The first multiplier is configured to attach the multi-carrier signal to the second training sequence to obtain a new multi-carrier signal. The second multiplier is configured to attach the new multi-carrier signal output by the first multiplier to the second training sequence to obtain an interference signal. The phase shifting circuit is configured to convert the phase of the interference signal output by the second multiplier to obtain the opposite of the interference signal. The buffer is used to buffer the multi-carrier signal. The adding circuit is configured to add the opposite number of the interference signal to the multi-carrier signal buffered by the buffer to eliminate the interference signal.
本發明一實施方式所提供的訊號收發系統，包括訊號發送電路、多載波干擾消除電路、頻率偏移估測電路及訊號接收電路。訊號發送電路用於將多載波訊號附上第一訓練序列再送出。多載波干擾消除電路用於經由通訊通道從訊號發送電路接收附上第一訓練序列的多載波訊號，並消除其他系統對多載波訊號的干擾訊號。頻率偏移估測電路用於估測已消除干擾訊號的多載波訊號的頻率偏移。訊號接收電路用於接收頻率偏移估測電路所輸出的多載波訊號。其中，多載波干擾消除電路包括訓練序列產生電路、第一乘法器、第二乘法器、移相電路、緩衝器及加法電路。訓練序列產生電路用於產生第二訓練序列，第二訓練序列與第一訓練序列正交。第一乘法器用於將多載波訊號附上第二訓練序列，以得到新多載波訊號。第二乘法器用於將第一乘法器輸出的新多載波訊號附上第二訓練序列，以得到干擾訊號。移相電路用於轉換第二乘法器輸出的干擾訊號的相位，以獲得干擾訊號的相反數。緩衝器用於緩存多載波訊號。加法電路用於將緩衝器所緩存的多載波訊號附上干擾訊號的相反數，以消除干擾訊號。A signal transceiving system according to an embodiment of the present invention includes a signal transmitting circuit, a multi-carrier interference canceling circuit, a frequency offset estimating circuit, and a signal receiving circuit. The signal transmitting circuit is configured to attach the multi-carrier signal to the first training sequence and send it again. Multi-carrier dryThe interference cancellation circuit is configured to receive the multi-carrier signal with the first training sequence from the signal transmitting circuit via the communication channel, and eliminate the interference signal of the other system to the multi-carrier signal. The frequency offset estimation circuit is used to estimate the frequency offset of the multi-carrier signal from which the interference signal has been cancelled. The signal receiving circuit is configured to receive the multi-carrier signal output by the frequency offset estimation circuit. The multi-carrier interference cancellation circuit includes a training sequence generating circuit, a first multiplier, a second multiplier, a phase shifting circuit, a buffer, and an adding circuit. The training sequence generation circuit is operative to generate a second training sequence that is orthogonal to the first training sequence. The first multiplier is configured to attach the multi-carrier signal to the second training sequence to obtain a new multi-carrier signal. The second multiplier is configured to attach the new multi-carrier signal output by the first multiplier to the second training sequence to obtain an interference signal. The phase shifting circuit is configured to convert the phase of the interference signal output by the second multiplier to obtain the opposite of the interference signal. The buffer is used to buffer the multi-carrier signal. The adding circuit is configured to add the opposite number of the interference signal to the multi-carrier signal buffered by the buffer to eliminate the interference signal.
藉由以下對具體實施方式詳細的描述並結合附圖，將可輕易的瞭解上述內容及此項發明之技術效果。The above and the technical effects of the invention can be easily understood from the following detailed description of the embodiments and the accompanying drawings.
10‧‧‧訊號收發系統10‧‧‧Signal Transceiver System
12‧‧‧訊號發送電路12‧‧‧Signal Transmitting Circuit
14‧‧‧多載波干擾消除電路14‧‧‧Multi-carrier interference cancellation circuit
16‧‧‧頻率偏移估測電路16‧‧‧frequency offset estimation circuit
18‧‧‧訊號接收電路18‧‧‧Signal receiving circuit
140‧‧‧訓練序列產生電路140‧‧‧ Training sequence generation circuit
141‧‧‧第一乘法器141‧‧‧first multiplier
142‧‧‧第二乘法器142‧‧‧Second multiplier
143‧‧‧移相電路143‧‧‧ Phase shifting circuit
144‧‧‧緩衝器144‧‧‧buffer
145‧‧‧加法電路145‧‧‧Addition circuit
圖1為本發明訊號收發系統一實施方式的模組圖。1 is a block diagram of an embodiment of a signal transceiving system of the present invention.
圖2為圖1所示的多載波干擾消除電路一實施方式的具體電路圖。2 is a detailed circuit diagram of an embodiment of the multi-carrier interference cancellation circuit shown in FIG. 1.
請參閱圖1，所示為本發明訊號收發系統10一實施方式的模組圖。Referring to FIG. 1, a block diagram of an embodiment of a signal transceiving system 10 of the present invention is shown.
訊號收發系統10包括訊號發送電路12、通訊通道13、多載波干擾消除電路14、頻率偏移估測電路16及訊號接收電路18。在本實施方式中，訊號發送電路12將多載波訊號s(n)經由通訊通道13發送給訊號接收電路18，此時，多載波訊號s(n)經過通訊通道13已成為多載波訊號r(n)。在本實施方式中，多載波訊號為正交頻分複用(Orthogonal Frequency Division Multiplexing，OFDM)訊號，通訊通道13為加性白高斯雜訊(Additive White Gaussion Noise，AWGN)通道。The signal transceiving system 10 includes a signal transmitting circuit 12, a communication channel 13, a multi-carrier interference canceling circuit 14, a frequency offset estimating circuit 16, and a signal receiving circuit 18. In the present embodiment, the signal transmitting circuit 12 transmits the multi-carrier signals (n ) to the signal receiving circuit 18 via the communication channel 13 . At this time, the multi-carrier signals (n ) has become the multi-carrier signalr through the communication channel 13 (n ). In this embodiment, the multi-carrier signal is an Orthogonal Frequency Division Multiplexing (OFDM) signal, and the communication channel 13 is an Additive White Gaussian Noise (AWGN) channel.
在本實施方式中，訊號發送電路12與訊號接收電路18的多載波訊號s(n)與r(n)之間存在本地振盪器不匹配而造成的頻率偏移ε，並且受到其他系統的干擾訊號，訊號接收電路18所接收的多載波訊號r(n)等於訊號發送電路12所發射的訊號s(n)乘上頻率偏移所造成的相位旋轉及加上雜訊n(n)、其他系統的干擾訊號I(n)，具體如(1)式
其中j表示虛數，N為多載波訊號的多載波個數，n(n)為複數白色高斯雜訊，其期望值(mean)為0，變異數(variance)為，且實部與虛部互為獨立。Where j is an imaginary number, N is the number of multicarriers of the multicarrier signal,n (n ) is a complex white Gaussian noise, and the expected value (mean) is 0, and the variance is And the real and imaginary parts are independent of each other.
訊號發送電路12用於將多載波訊號s(n)附上第一訓練序列c(n)並經由通訊通道13送出。在本實施方式中，訊號發送電路12藉由乘法器將多載波訊號s(n)與第一訓練序列c(n)相乘，以將多載波訊號s(n)附上一串第一訓練序列c(n)，即訊號發送電路12所傳送出去的多載波訊號為s(n)c(n)。The signal transmitting circuit 12 is configured to attach the multi-carrier signals (n ) to the first training sequencec (n ) and send it via the communication channel 13 . In the present embodiment, the signal transmitting circuit 12 multiplies the multi-carrier signals (n ) by the first training sequencec (n ) by a multiplier to attach the multi-carrier signals (n ) to a series of first training. The sequencec (n ), that is, the multi-carrier signal transmitted by the signal transmitting circuit 12 iss (n )c (n ).
多載波干擾消除電路14用於經由通訊通道13從訊號發送電路12接收附上一串第一訓練序列c(n)的多載波訊號r(n)，並消除其他系統對多載波訊號r(n)的干擾訊號I(n)。在本實施方式中，多載波干擾消除電路14經由通訊通道13從訊號發送電路12接收附上第一訓練序列後的多載波訊號。訊號發送電路12附上第一訓練序列c(n)後所傳送的多載波訊號s(n)c(n)經過AWGN通道後可表示成：
其中，c(n)為統計獨立的M-ary相移鍵控(Phase Shift Keying，PSK)訊號，且|c(n)|2=1，θ0為未知的初始相位，為正規化頻率偏移。此時，根據Tretter’s雜訊近似理論，可將(2)式改寫成：
令
其中，。此時，因多載波干擾消除電路14所接收的多載波訊號r(n)處於高訊雜比的條件下，雜訊功率很小，所以(4)式可近似成
其中，among them,
由(5)式可知，當複數白色高斯雜訊近似成相位雜訊時，多載波干擾消除電路14所接收的多載波訊號r(n)可表示成多載波訊號s(n)．c(n)旋轉相位加上干擾訊號I(n)，即：
請參閱圖2，為圖1所示的多載波干擾消除電路14的具體電路圖。在本實施方式中，多載波干擾消除電路14包括訓練序列產生電路140、第一乘法器141、第二乘法器142、移相電路143、緩衝器144及加法電路145。Please refer to FIG. 2 , which is a specific circuit diagram of the multi-carrier interference cancellation circuit 14 shown in FIG. 1 . In the present embodiment, the multicarrier interference canceling circuit 14 includes a training sequence generating circuit 140, a first multiplier 141, a second multiplier 142, a phase shifting circuit 143, a buffer 144, and an adding circuit 145.
訓練序列產生電路140用於產生第二訓練序列b(n)，其中第二訓練序列b(n)與第一訓練序列c(n)呈現正交關係，且|b(n)|2=1。Training sequence generating circuit 140 for generating a second training sequenceb(n), wherein the second training sequenceb(n) with a first training sequencec(n) exhibits an orthogonal relationship, and| b (n) | 2 = 1 .
第一乘法器141用於將多載波干擾消除電路14所接收的多載波訊號r(n)附上第二訓練序列b(n)，以得到新多載波訊號y(n)。在本實施方式中，第一乘法器141將第二訓練序列b(n)與多載波訊號r(n)相乘，可得
因第二訓練序列b(n)與第一訓練序列c(n)呈現正交關係，所以(7)式可轉換為y(n)=b(n)．I(n)。Since the second training sequenceb (n ) exhibits an orthogonal relationship with the first training sequencec (n ), the equation (7) can be converted toy (n )=b (n ).I (n ).
第二乘法器142用於將第一乘法器141輸出的新多載波訊號y(n)附上第二訓練序列b(n)。在本實施方式中，第二乘法器142將第二訓練序列b(n)與新多載波訊號y(n)相乘，由於|b(n)|2=1，可得y(n)．b(n)=|b(n)|2．I(n)=I(n) (8)The second multiplier 142 for a new multi-carrier signaly(n) output from the first multiplier 141 attached second training sequenceb(n). In the present embodiment, the second multiplier 142 multiplies the second training sequenceb (n ) by the new multicarrier signaly (n ), and since |b (n )|2 = 1,y (n ) is obtained.b (n )=|b (n )|2 .I (n )=I (n ) (8)
此時，可知第二乘法器142輸出的即為其他系統對r(n)的干擾訊號I(n)。In this case, it is understood other systems is the output of the second multiplier 142r(n) of the interference signalI(n).
移相電路143用於轉換第二乘法器輸出的干擾訊號I(n)的相位，以獲得干擾訊號的相反數-I(n)。The phase shifting circuit 143 is configured to convert the phase of the interference signalI (n ) output by the second multiplier to obtain the inverse of the interference signal -I (n ).
緩衝器144用於緩存多載波干擾消除電路14所接收的多載波訊號r(n)。The buffer 144 is used to buffer the multi-carrier signalr (n ) received by the multi-carrier interference cancellation circuit 14.
加法電路145用於將移相電路143所輸出的-I(n)附加到緩衝器144所輸出的r(n)，以消除干擾訊號I(n)。在本實施方式中，加法電路145藉由加法器將(6)式與移相電路143所輸出的-I(n)相加，可得
此時，由(9)式可知，已將多載波干擾消除電路14所接收的多載波訊號r(n)中的干擾訊號I(n)消除，多載波干擾消除電路14所輸出的多載波訊號z(n)已經不包括干擾訊號I(n)。At this time, it can be seen from equation (9) that the interference signalI (n ) in the multi-carrier signalr (n ) received by the multi-carrier interference cancellation circuit 14 has been cancelled, and the multi-carrier signal output by the multi-carrier interference cancellation circuit 14 is cancelled.z (n ) does not include the interference signalI (n ).
頻率偏移估測電路16用於估測經多載波干擾消除電路14消除干擾訊號的多載波訊號z(n)的頻率偏移。The frequency offset estimation circuit 16 is configured to estimate the frequency offset of the multi-carrier signalz (n ) that cancels the interference signal by the multi-carrier interference cancellation circuit 14.
訊號接收電路18用於接收頻率偏移估測電路16所輸出的多載波訊號。The signal receiving circuit 18 is configured to receive the multi-carrier signal output by the frequency offset estimation circuit 16.
本發明實施方式所提供的多載波干擾消除電路14及使用其的訊號收發系統10採用簡單的乘法、移相以及加法等電路，成功地消除了多載波訊號中的干擾訊號，從而大大提升後續多載波頻率估測的精確度，有效提升OFDM技術的傳輸效率。The multi-carrier interference cancellation circuit 14 and the signal transceiving system 10 using the same according to the embodiments of the present invention successfully eliminate the interference signals in the multi-carrier signal by using simple multiplication, phase shifting, and addition circuits, thereby greatly improving the subsequent multi-carrier signals. The accuracy of carrier frequency estimation effectively improves the transmission efficiency of OFDM technology.
綜上所述，本發明符合發明專利要件，爰依法提出專利申請。惟，以上所述者僅為本發明之較佳實施例，舉凡熟悉本案技藝之人士，在爰依本案發明精神所作之等效修飾或變化，皆應包含於以下之申請專利範圍內。In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art of the present invention should be included in the following claims.
14‧‧‧多載波干擾消除電路14‧‧‧Multi-carrier interference cancellation circuit
140‧‧‧訓練序列產生電路140‧‧‧ Training sequence generation circuit
141‧‧‧第一乘法器141‧‧‧first multiplier
142‧‧‧第二乘法器142‧‧‧Second multiplier
143‧‧‧移相電路143‧‧‧ Phase shifting circuit
144‧‧‧緩衝器144‧‧‧buffer
145‧‧‧加法電路145‧‧‧Addition circuit
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| TW98121975ATWI474628B (en) | 2009-06-30 | 2009-06-30 | Multi-carrier interference eliminating circuit and signal transceiving system employing the same |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| TW98121975ATWI474628B (en) | 2009-06-30 | 2009-06-30 | Multi-carrier interference eliminating circuit and signal transceiving system employing the same |
| Publication Number | Publication Date |
|---|---|
| TW201101709A TW201101709A (en) | 2011-01-01 |
| TWI474628Btrue TWI474628B (en) | 2015-02-21 |
| Application Number | Title | Priority Date | Filing Date |
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| TW98121975ATWI474628B (en) | 2009-06-30 | 2009-06-30 | Multi-carrier interference eliminating circuit and signal transceiving system employing the same |
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