CN1156110C - Transmitting and zero intermediate frequency receiving method and device in multi-carrier CDMA system based on polyphase decomposition - Google Patents

Abstract

The present invention provides a transmitting and zero intermediate frequency receiving method based on a modulation type filter bank multicarrier DS-CDMA system and a simplification implementing method thereof for multiphase decomposition. The present invention has the essential schemes that a multicarrier DS-CDMA receiving signal is down converted to a baseband from radio frequency or high intermediate frequency on a receiving end so as to enable the central frequency of a middle carrier wave of a plurality of carrier waves to be zero frequency; lowest sampling frequency is used for sampling, and a modulation type filter bank is used for replacing a multicarrier digital filter; when a plurality of carrier wave receiving signals are separated and transmitting signals on each original carrier wave are reconstructed, a realization structure of a multiphase decomposition and simplification receiving machine is used for reducing the hardware realization complexity of the receiving machine; on a transmitting end, the modulation type filter bank is used for replacing the multicarrier digital filter likewise, and when information to be carried by each carrier wave passes through a modulation type send filter group, the realization structure of a multiphase decomposition and simplification transmitter is used; then, the information is simultaneously up converted to the high intermediate frequency or the radio frequency. The present invention mainly considers how to fully perform the capacity for digital processing in the multicarrier DS-CDMA system, and hardware sources are farthest saved, which enables the implementation of the system to be more economical and reliable.

Description

Multi-carrier CDMA system transmission and zero-IF reception method and device based on polyphase decomposition

(1) Technical field:

The invention belongs to the field of CDMA (Code Division Multiple Access) cellular communication systems, in particular to a multi-carrier CDMA system transmission and zero-IF reception method and device based on polyphase decomposition

(two) background technology:

CDMA cellular communication technology shows great development potential due to its simple frequency planning, large system capacity, strong anti-multipath ability, good communication quality, and low electromagnetic interference. It is the mainstream technology of future mobile communication including the third generation. Among them, the multi-carrier DS-CDMA (Direct Sequence Spread Spectrum Code Division Multiple Access) system has the outstanding advantages of supporting high-speed data transmission, high frequency band utilization, effective frequency diversity and time diversity, and effective suppression of interference. .

Traditional multi-carrier DS-CDMA receivers use high-Q high-frequency analog matched filters equal to the number of carriers to separate signals transmitted on different carrier frequencies; and then down-convert the RF signals on each carrier to baseband; and then sample each carrier signal at a low frequency. The number of sets of radio frequency analog circuits required by such a receiver is equal to the number of carriers; and the minimum sampling rate is twice the signal bandwidth. The present invention proposes a zero-IF receiving method in which each carrier signal is simultaneously down-converted from a radio frequency or an IF (IF means that the frequency of the IF used is much higher than the bandwidth of the modulation signal) to the baseband by using only one set of analog receiving circuits. The zero intermediate frequency here means that the result of down-conversion is that the center frequency of a carrier in the middle of multiple carriers is zero frequency. The zero-IF receiver has the following advantages: (1) It does not require a high-Q high-frequency matched filter. However, high-frequency filters are still used in zero-IF receivers to reduce the requirements on the dynamic range of down-conversion and prevent mixing of RF signals and harmonic components of local oscillators. (2) Due to the use of zero intermediate frequency reception, the low-pass filter is easily integrated into the chip, and the digital filter is used to give full play to the advantages of digital processing. (3) Since the zero-IF signal is a complex signal, the requirement for sampling frequency can be reduced as much as possible during subsequent digital processing, and the difficulty of hardware implementation can be reduced. (4) From the perspective of software radio, the use of zero-IF receiver will make the digital processing part after A/D sampling and RAKE receiver can be easily designed as a single-chip receiver, only one radio frequency processing device and A/D D converter device.

(3) Contents of the invention:

The purpose of the present invention is to address the deficiencies of the existing multi-carrier DS-CDMA system transmission and reception technology, to propose a practical transmission and reception technology that can fully utilize the digital processing capability and reduce the hardware scale as much as possible, so that the realization of the system More economical and reliable.

The present invention proposes a multi-carrier DS-CDMA system transmission and zero-IF receiving method based on a modulated filter bank and a simplified implementation method of polyphase decomposition thereof. The technical scheme is: at the receiving end, the multi-carrier DS-CDMA The received signal is down-converted from radio frequency or high-frequency to baseband, so that the center frequency of a carrier in the middle of multiple carriers is zero frequency, and the lowest sampling frequency is used for sampling, and the multi-carrier digital filter is replaced by a modulated filter bank. While separating multiple carrier receiving signals and reconstructing the original sending signals on each carrier, polyphase decomposition is used to simplify the implementation structure of the receiver and reduce the hardware implementation complexity of the receiver. At the sending end, the multi-carrier digital filter is also replaced by a modulated filter bank. While the information pre-carried by each carrier passes through the modulated transmit filter bank in parallel, the implementation structure of the transmitter is simplified by polyphase decomposition, and then simultaneously Upconversion to IF or RF.

Now illustrate its realization device in conjunction with accompanying drawing:

The simplified implementation of the multi-carrier DS-CDMA system based on the transmission of the modulated filter bank and the reception method of zero-IF and its polyphase decomposition includes the following steps: at the receiving end, the multi-carrier signal is directly down-converted from the radio frequency or high-frequency to Baseband; sampling baseband multi-carrier received signals; using digital filters to form a modulated filter bank structure. At the transmitting end, digital filters are used to form a modulated transmit filter bank structure; the information pre-carried by each carrier is passed through the modulated transmit filter bank in parallel, and then up-converted to radio frequency or high-frequency at the same time. The modulated filter banks at the two ends of the transmitter and receiver are simplified and realized by polyphase decomposition. Each will be specifically described.

1. Transmission and zero-IF reception method based on modulated filter bank

At the receiving end, the received signal of multi-carrier DS-CDMA is down-converted from radio frequency or high-frequency to baseband first, so that the center frequency of the middle carrier among the multiple carriers is at zero frequency, and then filtered out by a low-pass filter. external noise.

Taking cdma2000 system three-carrier configuration cdma2000-3x as an example, the implementation method of zero-IF reception is explained in detail. Figure 1(a) is a schematic diagram of the frequency spectrum of the three carrier signals at the receiving end. The center frequencies of the three carriers are f ₁ , f ₂ , f ₃ respectively, and they satisfy

f ₁ +f _Δ =f ₂ =f ₃ -f _Δ [Formula 1]

where f _Δ =1.23 MHz. After down-conversion processing and low-pass filtering, the frequency spectrum of the three-carrier baseband signal shown in Figure 1(b) is obtained, and the center frequency of the second carrier signal is zero.

A/D sampling is performed on the zero-IF baseband signal of the three carriers shown in Figure 1(b), and the sampled signal is sent to a complex coefficient digital filter equal to the number of carriers for processing to separate the signals carried by different carriers. , the resulting receiver is called a multi-carrier receiver structure based on a modulated filter bank.

At the transmitting end, the information pre-carried by each carrier is passed through a modulation-type transmitting filter bank composed of complex coefficient digital filters equal to the number of carriers in parallel to obtain a baseband signal with a spectrum as shown in Figure 1(b) ; and then up-convert to RF or IF at the same time. The up-converted signal has a frequency spectrum as shown in Fig. 1(a). The resulting transmitter is called a modulated filter bank based multi-carrier transmitter structure.

Taking the three-carrier configuration of the cdma2000 system as an example, the structure of the transmitter and zero-IF receiver based on the modulation filter bank is shown in Figure 2. If the channel is not distorted, using this structure can accurately reconstruct the original transmitted signal on each carrier at the receiving end.

分别表示在接收机中重建的各载波上的信息。↑M表示M倍上采样，↓M表示M倍下采样。在cdma2000系统三载波配置中，M＝4；H_k(z)，k＝-1，0，1分别对应第一、二、三载波信号所需的数字滤波器；H₀(z)为低通原型数字滤波器，其冲激响应系数为h(n)。各滤波器的冲激响应系数分别为：In Figure 2, p ₁ , p ₂ , and p ₃ represent the transmission information on each carrier respectively,

Represents the information on each carrier reconstructed in the receiver, respectively. ↑M means M times upsampling, ↓M means M times downsampling. In the three-carrier configuration of the cdma2000 system, M=4; H _k (z), k=-1, 0, and 1 respectively correspond to the digital filters required for the first, second, and third carrier signals; H ₀ (z) is low Through the prototype digital filter, its impulse response coefficient is h(n). The impulse response coefficients of each filter are:

$h_k\left(\mathrm{no}\right)=h\left(\mathrm{no}\right)e^{j\frac{\mathrm{\π}}{2}\mathrm{k\; n}}=h\left(\mathrm{no}\right)W_4^{\mathrm{k\; n}},k=-\mathrm{1,0,1}$ [Formula 3]

in $W_m=e^{j\frac{2\mathrm{\π}}{m}}.$

2. Simplified realization of the modulated filter bank at the receiving end

Suppose the order of the low-pass prototype digital filter impulse response h(n) given in [Equation 3] is L (for the three-carrier configuration in the cdma2000 system, the order L of the low-pass prototype digital filter at the sending end is taken as value is 48.), and its polyphase decomposition is:

$h\left(z\right)=\underset{\mathrm{no}=0}{\overset{L-1}{\mathrm{\Σ}}}h\left(\mathrm{no}\right)z^{-\mathrm{no}}=\underset{q=0}{\overset{3}{\mathrm{\Σ}}}{G}_q\left(z^4\right)z^{-q}$ [Formula 4]

Among them, the qth polyphase element of the low-pass prototype filter H(z) is:

$G_q\left(z\right)=\underset{p=0}{\overset{L/4-1}{\mathrm{\Σ}}}h(4p+q)z^{-p}$ [Formula 5]

Then the polyphase decomposition of each filter is:

$h_k\left(z\right)=\underset{q=0}{\overset{3}{\mathrm{\Σ}}}{G}_q\left(z^4\right)W_4^{\mathrm{kq}}{z}^{-q},k=-\mathrm{1,0,1}$ [Formula 6]

Express the above formula in the form of multiplying two matrices:

$\left[\begin{array}{c}{h}_{-1}\left(z\right)\\ h_0\left(z\right)\\ h_1\left(z\right)\end{array}\right]\left[\begin{array}{cccc}{W}_4^0& W_4^{-1}& W_4^{-2}& W_4^{-3}\\ W_4^0& W_4^0& W_4^0& W_4^0\\ W_4^0& W_4^1& W_4^2& W_4^3\end{array}\right]\left[\begin{array}{cccc}{G}_0\left(z^4\right)& 0& 0& 0\\ 0& G_1\left(z^4\right)z^{-1}& 0& 0\\ 0& 0& G_2\left(z^4\right)z^{-2}& 0\\ 0& 0& 0& G_3\left(z^4\right)z^{-3}\end{array}\right]$ [Formula 7]

Thus, a simplified realization structure of the multi-phase decomposition of the receiving filter bank of the multi-carrier DS-CDMA system is obtained, as shown in FIG. 3 .

The matrix T in Figure 3 is:

$T=\left[\begin{array}{cccc}{W}_4^0& W_4^{-1}& W_4^{-2}& W_4^{-3}\\ W_4^0& W_4^0& W_4^0& W_4^0\\ W_4^0& W_4^1& W_4^2& W_4^3\end{array}\right]=\left[\begin{array}{cccc}1& -j& -1& \mathrm{<figure-callout\; id="1"\; label="j"\; filenames="C0210042800102.png,C0210042800111.png"\; state="\{\{state\}\}">j</figure-callout>}\\ 1& 1& 1& 1\\ 1& j& -1& -j\end{array}\right]$ [Formula 8]

3. Simplified realization of the modulation filter bank at the sending end

Similarly, from Figure 2 and [Equation 7], the simplified implementation structure of the polyphase decomposition of the transmit filter bank of the multi-carrier DS-CDMA system can be obtained, as shown in Figure 4. The matrix T ^H in Figure 4 represents the conjugate transpose of the matrix T, and the specific values are as follows:

$T^h=\left[\begin{array}{ccc}1& 1& 1\\ j& 1& -j\\ -1& 1& -1\\ -\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="C0210042800102.png,C0210042800111.png"\; state="\{\{state\}\}">j</figure-callout>}& 1& +j\end{array}\right]$ [Formula 9]

4. Comparison of Computational Complexity

Taking the three-carrier configuration of the cdma2000 system as an example, the superior characteristics of the present invention in reducing the implementation complexity are illustrated. The number of multiply-accumulates required for each input sample processing is used as a measure of the complexity of the implementation.

For a three-carrier receiver, if the structure shown in Figure 2 is used to implement, the number of times of multiplication and accumulation required for each input sample is 3L. If the polyphase decomposition shown in Figure 4 is used to simplify the receiving structure, since all filtering operations only need to be performed at 1/M times the sampling rate, and the M filters are polyphase elements of the low-pass prototype filter, the The total length is L. Considering that the operation matrix T shown in [Equation 8] does not require multiplication, so for each sampled input signal, the number of times of multiplication and accumulation required by the polyphase decomposition receiving structure shown in Figure 4 is: L multiplication and accumulation operations and 12 addition operation. It can be seen that the receiver structure based on polyphase decomposition can reduce the implementation complexity by about 3M=12 times on the basis of the receiving structure shown in FIG. 2 .

Similar results can be obtained for the sender. The implementation complexity of the transmitting device using multi-phase decomposition can be reduced by about 3M=12 times compared with the direct implementation shown in FIG. 2 .

Beneficial effects of the present invention: Aiming at the multi-carrier DS-CDMA system, the present invention proposes a sending and receiving method that can give full play to the digital processing capability and save hardware resources to the greatest extent. Its basic feature is that the digital processing technology of the modulated filter bank is used at the sending end and the receiving end, without the need for multiple parallel analog processing devices, so that the realization of the system is more economical and reliable. The multi-phase decomposition is used to decompose and simplify the multiple filters required by the transmitting end and the receiving end, which reduces the complexity of implementation. The invention can be used in any multi-carrier mobile communication system including cdma2000-3x.

(4) Description of drawings:

Fig. 1 (a) is the radio frequency (or intermediate frequency) spectrum schematic diagram of three carrier signals, (b) is the three carrier baseband signal spectrum schematic diagrams;

Fig. 2 is the structural representation of the modulated filter bank of the sending and receiving of three carriers;

Fig. 3 is the simplified realization structure of the polyphase decomposition of multi-carrier DS-CDMA system receive filter bank;

Fig. 4 is the simplified implementation structure of the polyphase decomposition of the multi-carrier DS-CDMA system transmit filter bank;

5 is a block diagram of a multi-carrier DS-CDMA system receiving device based on polyphase decomposition;

Fig. 6 is a block diagram of a multi-carrier DS-CDMA system transmission device based on polyphase decomposition;

Figure 7 Implementation example of multi-carrier DS-CDMA system transmission device based on polyphase decomposition

Figure 8 is an implementation example of a multi-carrier DS-CDMA system zero-IF receiving device based on polyphase decomposition.

(5) Specific implementation methods:

Further illustrate the implementing device of the present invention below in conjunction with accompanying drawing and embodiment

The down-sampling device (device 1) samples every M input data to obtain a data output. The up-sampling device (device 2 ) samples each input data once and outputs the data, and outputs M-1 zeros continuously before sampling the next input data. The filter device (device 3) is an FIR filter, and the dependence between its impulse response coefficient and the prototype filter h(n) of the system is shown in [Formula 5]. The matrix operation device (device 4/device 5) completes the multiplication operation of two matrices as shown in [Formula 7].

Fig. 5 is based on the receiving device block diagram of the multi-carrier CDMA system of polyphase decomposition, and it is by M times downsampling device (device 1), filter device (device 3), time delay device and matrix computing device (device 4) totally four Composition of a processing device. For the M times downsampler device (device 1), its input is the data after A/D sampling, and it samples every M input data to obtain a data output. As for the filter means (device 3), it filters the data from the M-fold downsampler means to perform FIR filtering as shown in [Equation 5]. As for the matrix operation means (device 4), its input comes from the filtered outputs of the M filter means, and performs the matrix operation as shown in [Formula 7]. For the cdma2000-3x system, its operation matrix T is shown in [Formula 8].

Fig. 6 is based on the transmission device block diagram of the multi-carrier CDMA system of polyphase decomposition, and it is by M times upsampler device (device 2), filter device (device 3), time delay device, adder and matrix operation device (device 5 ) consists of five processing devices. For the matrix operation device (device 5), its input is the information carried in advance by each carrier, and completes the matrix operation shown in [Formula 7]. For the cdma2000-3x system, its operation matrix is as shown in [Formula 9] T ^H , the operation results are correspondingly sent to M filter devices. For the filter device (device 3), it filters the data from the matrix operation device (device 5), completes the FIR filtering shown in [Formula 5], and outputs the result to the M times upsampler device (device 2 ). For the M-fold upsampler device (device 2), its input is the filtered data, it samples each input data once and outputs the data, and continuously outputs M-1 before sampling the next input data zero. The outputs of the M upsampler devices are respectively output after being delayed and added as shown in FIG. 6 .

FIG. 7 and FIG. 8 are respectively schematic diagrams of a multi-carrier DS-CDMA system based on polyphase decomposition and a zero-IF receiving device implemented in a cdma2000-3x system. The implementation example of the transmitting device shown in FIG. 7 includes a transmitting device for polyphase decomposition of a modulated filter bank, a D/A conversion device and a radio frequency processing device. Among them, the radio frequency processing device completes the up-conversion processing of the output signal of the transmitting device for polyphase decomposition of the modulated filter bank, that is, modulates the baseband D/A output signal to an intermediate frequency or radio frequency. The implementation example of the receiving device shown in Fig. 8 includes a radio frequency front-end device, an A/D sampling device, a device for implementing polyphase decomposition of a modulated filter bank, and a multipath RAKE receiving device. Among them, the radio frequency front-end device completes the down-conversion processing of the received radio frequency or high-frequency multi-carrier signal, makes the center frequency of the intermediate carrier be zero frequency, and performs low-pass filtering on the baseband signal after the down-conversion process. The A/D sampling device completes the sampling output of the baseband multi-carrier signal, and its sampling frequency is 4×1.2288Msps, and the sampling output is sent to the realization device of polyphase decomposition of the modulation filter bank in serial mode. The RAKE receiver completes the multipath combined reception of a single carrier signal.

Claims (2)

1. based on the multi-carrier CDMA system transmission of heterogeneous decomposition and the method for reseptance of zero intermediate frequency, it is characterized in that: at receiving terminal, at first many radio frequencies of multicarrier DS-CDMA received signal or high intermediate frequency are downconverted to base band, so that the centre frequency of a carrier wave of the centre of a plurality of carrier waves is a zero frequency, filter out-of-band noise through low pass filter then; At transmitting terminal, with the modulation type bank of filters information parallel passes modulation type transmitting filter group that each carrier wave carries is in advance obtained baseband signal, upconvert to high intermediate frequency or radio frequency then.

2. based on the multi-carrier CDMA system transmission of heterogeneous decomposition and the receiving system of zero intermediate frequency, it is characterized in that: receiving system is made up of M times of down-sampler device, filter apparatus, time-delay mechanism and matrix operating device, data after wherein M times of down-sampler device input sampled through A/D, and once to every M input data sampling, obtain data and export to filter apparatus, filter apparatus carries out filtering to the data from M times of down-sampler device, and export to matrix operating device, finish matrix operation; Dispensing device is by M times of up-sampler device, filter apparatus, time-delay mechanism, adder and matrix operating device are formed, wherein matrix operating device is imported the information that each carrier wave carries in advance, and finish matrix operation, its operation result is sent to M filter apparatus, filter tired apparatus the data from matrix operating device are carried out filtering, and the result outputed to M times of up-sampler device, M times of up-sampler device input is through filtered data, to each input data sampling once and export this data, and it is individual zero to export M-1 before to next sampling input data more continuously, and respectively through exporting after corresponding time-delay mechanism and the adder addition.

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