JP2013201775A - Transmitter device - Google Patents

Abstract

A transmission device that realizes flat amplitude characteristics in a frequency band is provided.
In order to solve the above-mentioned problem, the present invention is a transmission apparatus constituting a communication apparatus on the transmission side of a DS-CDMA communication system, and a modulation section 10 for performing modulation processing on information to be transmitted A spread processing unit 20 that spreads the modulated signal using a phase rotation sequence having periodicity in units of spreading factor, and a frequency conversion unit 40 that performs frequency conversion on the spread signal. It is characterized by that.
[Selection] Figure 1

Description

  The present invention relates to a transmission apparatus that supports a CDMA (Code Division Multiple Access) system that performs spread spectrum directly using a code sequence.

  A conventional communication apparatus that supports direct spread (DS) CDMA (hereinafter referred to as DS-CDMA) includes, for example, a modulator, a multiplier that multiplies a code sequence, and a baseband signal as an RF signal. Transmitter including frequency converter and amplifier for conversion, amplifier, frequency converter for converting RF signal to baseband signal, receiver including correlator and demodulator for multiplying by code sequence and integrating corresponding to one symbol And consisted of.

  The operation of the conventional communication apparatus having the above configuration will be described. In the transmitter, transmission information is input to the modulation unit, and the modulation unit modulates the input information to generate a modulated signal. The modulation signal output from the modulation unit is multiplied by a code sequence in a multiplier and spread-modulated into a wideband signal. The spread-modulated signal is frequency-converted to an RF signal by a frequency converter, further amplified by an amplifier, and then transmitted from an antenna to a facing communication device (receiver). On the other hand, the receiver receives a signal from a communication device (transmitter) facing each other with an antenna, and the received signal is amplified by an amplifier. The amplified received RF signal is frequency-converted to a baseband signal by a frequency converter, then multiplied by a code sequence in a correlator, and subjected to a correlation operation for integration in symbol units, and a correlation value is output. Is done. The correlation value is demodulated by the demodulator, and the transmitted information is reproduced. In general, the demodulation unit is configured to obtain a path diversity effect by RAKE combining processing in order to support a multipath transmission path.

Mitsuo Yokoyama “Spread Spectrum Communication System” Science and Technology Publishers (1988)

  In wideband transmission by the DS-CDMA system, it is affected by multipath delay waves during radio wave propagation. One of the methods for reducing the influence of the multipath delay wave is a method of obtaining a path diversity gain by RAKE combining the multipath delay wave on the receiving side, but if the number of multipath waves increases, all paths are increased. Cannot be combined, and the configuration of the demodulator that performs RAKE combining becomes complicated. Therefore, a technique for equalizing multipath delayed waves in the frequency domain (hereinafter referred to as frequency domain equalization) has been studied.

  However, when performing frequency domain equalization, it is necessary to estimate the channel impulse response in the frequency domain using a pilot symbol that is a known sequence. There is a problem that it is necessary to have a flat amplitude characteristic, and when applied to DS-CDMA, a code sequence and a pilot symbol having good correlation characteristics must be used.

  Further, when a cyclic prefix (sometimes referred to as CP) is added to each symbol block as a countermeasure against multipath delay waves by frequency domain equalization, the CP and the rear part of the symbol block are realized in order to realize synchronization of the symbol blocks. And the synchronization timing is estimated. However, since the CP and the rear part of the symbol block are also affected by the multipath delay wave, the correlation characteristic deteriorates and the synchronization timing estimation accuracy deteriorates. There was a problem.

  In addition, when a plurality of users are multiplexed and transmitted in DS-CDMA (a plurality of users transmit at the same time), orthogonal codes such as Walsh codes are assigned for each user, but the codes are basically binary. Therefore, depending on the modulation method for modulating information, the vector of the modulated signal may be combined in the same direction during user multiplexing. For this reason, there is a problem that it is necessary to increase the peak factor of the transmission signal, and the power efficiency of the amplifier on the transmission side is deteriorated.

  Further, when a plurality of users are multiplexed and transmitted, there is a problem that it is difficult for the receiving side to accurately perform channel estimation for each user while maintaining orthogonality between users.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a transmission apparatus that realizes a flat amplitude characteristic on a frequency band in DS-CDMA communication. It is another object of the present invention to provide a transmission apparatus that can obtain a flat amplitude characteristic on a frequency band even when a code sequence is individually assigned to each user.

  Another object of the present invention is to obtain a transmission apparatus that realizes reduction of transmission peak power in a transmission / reception operation in which a plurality of users are multiplexed.

  Another object of the present invention is to provide a transmission apparatus that realizes communication capable of obtaining a channel estimation result for each user while maintaining orthogonality between users on the receiving side even in a transmission / reception operation in which a plurality of users are multiplexed. To do.

  In order to solve the above-described problems and achieve the object, the present invention is a transmission device that constitutes a communication device on the transmission side of a DS-CDMA communication system, and performs modulation processing on information to be transmitted. A spreading means for spreading the signal modulated by the modulating means using a phase rotation sequence having periodicity in units of spreading factor, and a frequency for performing frequency conversion on the signal spread by the spreading means Conversion means.

  According to the present invention, since the signal modulated by the modulating means is subjected to the spreading process using the phase rotation sequence having periodicity in units of spreading factor, the transmission peak power can be reduced. The effect that the amplitude characteristic on the frequency band can be made flat while maintaining the orthogonality between users, and the channel estimation can be performed accurately even when multipath delay waves exist on the receiving side. Play.

FIG. 1 is a diagram illustrating a configuration example of a transmission apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the first embodiment. FIG. 3 is a diagram showing an image of the frequency arrangement of the modulation signal determined by the user number. FIG. 4 is a diagram illustrating an example of a phase change of the phase rotation series C ₁ . FIG. 5 is a diagram illustrating another example of the phase change of the phase rotation series C ₁ . Figure 6 is a diagram showing the behavior and frequency spectrum on the frequency axis of the modulated signal corresponding to the phase rotation sequence C _2. Figure 7 is a diagram showing a frequency spectrum of phase rotation sequence C _2. FIG. 8 is a diagram illustrating a configuration example of the receiving device according to the first embodiment. FIG. 9 is a diagram illustrating a configuration example of the second embodiment of the transmission apparatus according to the present invention. FIG. 10 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the second embodiment. FIG. 11 is a diagram illustrating a configuration example of a receiving apparatus according to the second embodiment. FIG. 12 is a diagram illustrating a configuration example of an equalizer according to the second embodiment. FIG. 13 is a diagram illustrating a configuration example of a receiving apparatus according to the third embodiment. FIG. 14 is a diagram illustrating a configuration example of an equalizer according to the third embodiment. FIG. 15 is a diagram illustrating a configuration example of the transmission apparatus according to the fourth embodiment of the present invention. FIG. 16 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the fourth embodiment. FIG. 17 is a diagram illustrating a configuration example of a transmission apparatus according to the fifth embodiment. FIG. 18 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the fifth embodiment. FIG. 19 is a diagram illustrating a configuration example of a receiving apparatus according to the fifth embodiment. FIG. 20 is a diagram illustrating a configuration example of the equalizer of the fifth embodiment. FIG. 21A is a diagram for explaining the operation of the time domain mask processing unit. FIG. 21B is a diagram for explaining the operation of the time domain mask processing unit.

  Embodiments of a transmission apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a transmission apparatus according to a first embodiment of the present invention. The transmission apparatus according to the present embodiment includes a modulation unit 10, a spread processing unit 20, a waveform shaping filter 30, a frequency conversion unit 40, and an amplifier 50, and constitutes a signal transmission side communication apparatus in a DS-CDMA communication system. To do. The spread processing unit 20 also includes multipliers 21 and 22, which multiply the input signal by different phase rotation sequences C ₁ (φ _u ) and C ₂ (θ), respectively. Details of each phase rotation series will be described later.

FIG. 2 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the present embodiment. In FIG. 2, N _sym is the total number of symbols constituting a frame, N _k is the number of symbols (known symbols) constituting a known sequence part, N _d is the number of symbols (data symbols) constituting a data part, and SF is This is a spreading factor used in DS-CDMA.

The operation of the transmission apparatus shown in FIG. 1 will be described. An information sequence to be transmitted to the opposing communication device (receiving device) is input to the modulation unit 10, and the modulation unit 10 modulates the information sequence. The modulation signal output from the modulation unit 10 is input to the spread processing unit 20, where the multiplier 21 first causes the multiplier 21 to output a phase rotation sequence C ₁ (φ _u (j )) Is multiplied by the input signal. In Expression (1), u is a user number (u = 0 to N−1, N ≦ SF), and j is a chip number for each symbol (j = 0 to SF−1).

FIG. 3 is a diagram showing an image of the frequency arrangement of the modulation signal determined by the user number u. Specifically, the user-specific codes (codes # 0 to ##) corresponding to the phase rotation sequence C ₁ (φ) are shown. The frequency arrangement on the frequency axis of the modulation signal when N-1) is used is shown. As shown in the figure, the modulation signals are arranged to be orthogonal. FIG. 4 is a diagram illustrating an example of a phase change of the phase rotation series C ₁ .

As shown in FIG. 4, the phase rotation sequence C ₁ represented by the above equation (1) is a complex sequence whose phase changes in a sawtooth waveform in units of spreading factor SF. What is necessary for this complex sequence (C ₁ ) is that it has the property that the phase changes so as to have a sawtooth waveform in units of spreading factor SF. Therefore, for example, the symbol block may be a phase rotation sequence that changes in a sawtooth wave shape with the phase increasing in units of spreading factor SF as shown in FIG. 5 and the following equation (2). FIG. 5 is a diagram illustrating another example of the phase change of the phase rotation series C ₁ . In equation (2), u is a user number (u = 0 to N−1, N ≦ SF), i is a symbol number (i = 0 to N _sym −1), j is a chip number for each symbol (j = 0 to SF-1). When the phase rotation sequence having the properties as shown in FIGS. 4 and 5 is used, the phases become orthogonal between users.

The signal output from the multiplier 21 and multiplied by the phase rotation series C ₁ is input to the multiplier 22. The multiplier 22 multiplies the input signal from the multiplier 21 by a phase rotation sequence C ₂ (θ) expressed by the following equation (3), and converts the signal into a wideband signal. In the following equation (3), i is a symbol number (i = 0 to N _sym −1), j is a chip number for each symbol (j = 0 to SF−1), and m is an integer.

Here, the property of the phase rotation sequence C ₂ is that the frequency proportional to Bw / (N _sym · SF) between one symbol block as shown in the upper part of FIG. By Δf, it changes with a constant frequency change amount at intervals of the diffusion chip time. As a result, the output of the multiplier 22 has a frequency spectrum as shown in the lower part of FIG. Incidentally, FIG. 6 is a diagram showing the behavior and frequency spectrum on the frequency axis of the modulated signal corresponding to the phase rotation sequence C _2. As an example of a spreading sequence having such a property that the frequency constantly changes at such chip time intervals, it is generally expressed as the following equation (4). In the following equation (4), i is a symbol number (i = 0 to N _sym −1), j is a chip number (j = 0 to SF−1) for each symbol, and m and h are integers.

In particular, when the frame (known sequence + data portion) having the configuration shown in FIG. 2 is all “0”, the codes of the phase rotation sequences C ₁ and C ₂ are each cyclically increasing in phase in units of spreading factor SF. In the case where there is no multipath delayed wave, the multiplier 22 has the property of changing in a sawtooth waveform (C ₁ property) and the property of changing in the frequency band Bw (C ₂ property). The output (output of the spread processing unit 20) has a flat frequency spectrum as shown in FIG. 7, and the multipath delay wave can be accurately separated in the frequency domain. As a result, channel estimation accuracy can be improved. Note that FIG. 7 is a diagram showing the frequency spectrum of the phase rotation sequence C _2.

  The modulated signal spread in a wide band by the spread processing unit 20 is input to the waveform shaping filter 30, and after waveform shaping, the frequency is converted by the frequency conversion unit 40 and input to the amplifier 50. The output of the amplifier 50 is transmitted to the opposing communication device via the antenna.

Next, the operation of the receiving device (opposing communication device) that receives the signal transmitted from the transmitting device described above will be described. FIG. 8 is a diagram illustrating a configuration example of a receiving apparatus (receiving apparatus according to the first embodiment) which is a communication counterpart (opposing communication apparatus) of the transmitting apparatus illustrated in FIG. The receiving apparatus includes a frequency conversion unit 60, a waveform shaping filter 70, a despreading processing unit 80, and a demodulation unit 90. The despreading processing unit 80 includes a multiplier 81 and a correlator 82. The multiplier 81 multiplies the input signal by an antiphase rotation sequence D ₂ (−θ). Further, the correlator 82 performs correlation processing of the input signal using the anti-phase rotation sequence D ₁ (−φ _u ). These anti-phase rotation sequences are phase rotation sequences having properties opposite to those of the phase rotation sequences multiplied by the spreading processing unit 20 of the transmission-side communication device (the transmission device shown in FIG. 1).

In the receiving device, a signal from the opposing communication device (transmitting device) is received by the antenna, input to the frequency converting unit 60, and frequency-converted to a baseband signal. The baseband signal output from the frequency conversion unit 60 is filtered by the waveform shaping filter 70 and then input to the despreading processing unit 80. Despreading processing unit 80, first, a multiplier 81, multiplied by the inverse phase rotation sequence D ₂ represented by the following formula (5) to the input signal, giving a reverse rotation corresponding to the phase theta. In the formula (5), * is a symbol indicating a complex conjugate.
D ₂ = C ₂ ^* (5)

Next, in the despreading processing unit 80, the correlator 82 performs a despreading process on the output signal from the multiplier 81. Specifically, after the output signal from the multiplier 81 is multiplied by the antiphase rotation sequence D ₁ represented by the following equation (6), the reverse rotation corresponding to the phase φ _u is given, and then the spreading factor SF is equivalent. As many as the number of chips to be combined is synthesized in symbol units. Note that * is a symbol indicating a complex conjugate.
D ₁ = C ₁ ^* (6)

  The output from the correlator 82 (despreading processing unit 80) is input to the demodulating unit 90, where channel estimation is performed using the symbol portion of the known sequence in the frame (see FIG. 2), and the channel estimation result is used. After RAKE combining is performed, data is determined and a demodulation result is obtained.

As described above, the communication device (transmission device, reception device) of the present embodiment has a phase rotation sequence (C ₁ ) having periodicity in units of spreading factor and a phase rotation sequence that changes with a constant frequency width on the frequency axis. The spreading process is performed using (C ₂ ), and the despreading process is performed using the anti-phase rotation sequence (D ₁ , D ₂ ) having the opposite property to these phase rotation sequences. Thereby, the amplitude characteristic on the frequency band can be made flat while maintaining orthogonality between users, and channel estimation can be performed with high accuracy even when a multipath delayed wave exists.

  Also, in DS-CDMA, a code sequence having a unique orthogonal phase rotation among users is used for each symbol block as a code assigned to each user for user identification, so that signals can be separated between users. . Furthermore, the constellation of the signal after spreading processing basically rotates on the unit circle, so that the frequency of passing through the origin can be suppressed, and power efficiency can be improved in the amplifier of the transmission apparatus.

Embodiment 2. FIG.
In this embodiment, a communication device (transmitting device, receiving device) that performs transmission and reception by adding a symbolic cyclic prefix (CP) in DS-CDMA for frequency domain equalization will be described. Also, a communication apparatus that estimates synchronization timing without using correlation processing between a symbol block affected by a multipath delay wave and a rear part in order to realize symbol block synchronization will be described.

  FIG. 9 is a diagram illustrating a configuration example of the second embodiment of the transmission apparatus according to the present invention. As shown in the figure, the transmission apparatus of the present embodiment is obtained by replacing the diffusion processing unit 20 of the transmission apparatus described in the first embodiment (see FIG. 1) with a diffusion processing unit 20a. Further, the diffusion processing unit 20 a is obtained by adding a CP adding unit 23 to the diffusion processing unit 20. Since other components are the same as those of the transmission apparatus according to the first embodiment, the same reference numerals are given and description thereof is omitted.

  The CP adding unit 23 adds a symbol cyclic prefix (CP) to the output signal from the multiplier 22 and outputs the signal after adding the CP to the waveform shaping filter 30.

FIG. 10 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the second embodiment. In the transmission apparatus according to the present embodiment, as shown in FIG. 10, M (M is an arbitrary integer greater than or equal to 1) channel estimation slot and L (L is an arbitrary integer greater than or equal to 1) data. A frame having a configuration slot is transmitted. Both the channel estimation slot and the data slot included in this frame are composed of symbol blocks made up of N _sym + N _cp symbols. Here, N _cp is the number of symbols in the CP portion, SF is the spreading factor in DS-CDMA, N _sym is the number of symbols in the frequency domain conversion target portion, N _d is the number of data symbols, and N _k is the number of symbols in the known sequence portion. is there. As shown in FIG. 10, when N _k ≧ N _cp , the symbol of the CP portion can also be a completely known symbol. At this time, if the end portion of the pilot symbol and the known sequence portion are made exactly the same, the receiving side can perform correlation processing using a sequence of the CP portion prepared in advance. As a result, the synchronization timing can be estimated without being affected by the multipath delayed wave. Further, as shown in the first embodiment, if the pilot symbol part sequence is an all-zero pattern (corresponding to no modulation), it depends on the properties of the two phase rotation sequences C ₁ and C _2. Even when the pilot symbols are spread, the amplitude characteristics on the frequency band can be made flat, and channel estimation can be performed with high accuracy even when multipath delay waves are present.

  A diffusion processing unit 20a that performs an operation different from that of the transmission apparatus according to the first embodiment will be described. In the spread processing unit 20a, the output of the multiplier 22 is input to the CP adding unit 23. As shown in FIG. 10, the CP adding unit 23 copies the tail part of the slot and adds it as the CP to the head part of the slot. Is done. The signal to which the CP is added is output to the subsequent waveform shaping filter 30.

  Next, the operation of the receiving apparatus that receives a signal transmitted from the transmitting apparatus (see FIG. 9) according to the present embodiment will be described. FIG. 11 is a diagram illustrating a configuration example of a receiving apparatus according to the second embodiment. This receiving apparatus is obtained by replacing the despreading processing unit 80 of the receiving apparatus (see FIG. 8) described in Embodiment 1 with a despreading processing unit 80a. The despreading processing unit 80a is obtained by adding a CP removing unit 83 and an equalizer 84 to the despreading processing unit 80. Since other components are the same as those of the receiving apparatus of the first embodiment, the same reference numerals are given and description thereof is omitted.

  In the despreading processing unit 80a, the CP removal unit 83 receives the output signal of the waveform shaping filter 70, and removes the CP added to each slot for each slot or symbol block. The equalizer 84 equalizes the signal after the CP is removed by the CP removal unit 83.

FIG. 12 is a diagram illustrating a configuration example of the equalizer 84. As illustrated, the equalizer 84 includes a Nyquist point extraction unit 841 that extracts Nyquist points, FFT units 842 and 847 that convert time domain signals into frequency domain signals, and multipath delay based on channel estimation results. Compensator 843 that compensates for distortion caused by waves, IFFT unit 844 that converts a signal in the frequency domain into a signal in the time domain, and a multiplier 845 that multiplies the pilot sequence for one slot by an antiphase rotation sequence D _2. A multiplier 846 that multiplies the output signal from the multiplier 845 by the antiphase rotation sequence D ₁ , and a multiplier 848 that multiplies the output signal from the FFT unit 842 and the output signal from the FFT unit 847. . Multipliers 845 and 846 and FFT unit 847 constitute anti-phase rotation sequence generation unit 849 that generates a code sequence for despreading for one slot in the frequency domain.

  Despreading processing unit 80a that performs an operation different from that of the receiving apparatus according to Embodiment 1 will be described. In the despreading processing unit 80a, the CP removal unit 83 receives the output signal from the waveform shaping filter 70, and after removing the CP, inputs it to the equalizer 84 (see FIGS. 11 and 12). In the equalizer 84, the Nyquist point extraction unit 841 first extracts a Nyquist point sample from the signal after CP removal (output signal of the CP removal unit 83). The output of the Nyquist point extraction unit 841 is input to the FFT unit 842. The FFT unit 842 converts the input signal (Nyquist point sample signal) from a time domain sample to a frequency domain sample, and obtains an obtained signal (frequency domain). To the compensator 843 and the multiplier 848.

On the other hand, the inverse phase rotation sequence generation unit 849 generates a code sequence for despreading in the frequency domain. Specifically, first, a pilot sequence (for example, an all “0” pattern) having a number of samples of N _sym × SF is input to the multiplier 845, and an antiphase rotation sequence D ₂ = C ₂ ^* (C ₂ is a value of the transmitter). A reverse rotation process corresponding to the phase θ is performed using the phase rotation sequence multiplied by the multiplier 22 (* represents a complex conjugate). Further, the output of the multiplier 845 is input to the multiplier 846, and the anti-phase rotation sequence D ₁ = C ₁ ^* (C ₁ is a phase rotation sequence multiplied by the multiplier 21 of the transmission device, and * represents a complex conjugate. ) Is generated, an inverse phase rotation sequence for despreading for one slot (N _sym × SF samples) excluding the CP portion is generated. Furthermore, the output of the multiplier 846 is input to the FFT unit 847 and converted from the time domain to the frequency domain.

Multiplier 848 (corresponding to channel estimation means) outputs the N _sym × SF sample of the channel estimation slot among the inputs from FFT unit 842 and outputs the result from anti-phase rotation sequence generation unit 849 (FFT unit 847). A channel estimation value H (i) (i = 0 to N _sym · SF−1) in the frequency domain is calculated by multiplying the frequency-phase anti-phase rotation sequence. The channel estimation value H (i) is input to the compensation unit 843, and the compensation unit 843 compensates the input signal from the FFT unit 842 in the frequency domain. In the compensation method in the frequency domain performed by the compensation unit 843, for example, the data slot is determined by the compensation amount W (i) on the frequency domain in accordance with the MMSE (least square error) standard expressed by the following equation (7). Is subjected to distortion compensation processing due to multipath delay waves. In Equation (7), γ represents the ratio of signal power to noise power, and * is a symbol indicating complex conjugate.

  The output of the compensation unit 843 is input to the IFFT unit 844, converted from a frequency domain signal to a time domain signal, and then output to the subsequent multiplier 81 (see FIG. 11). The operations of the multiplier 81 and the correlator 82 are as described in the first embodiment.

  The output of the correlator 82 (despreading processing unit 80a) is input to the demodulating unit 90. The demodulating unit 90 performs estimation of the frequency deviation and channel estimation in the time domain using the symbol part of the known sequence in the frame. Then, based on the frequency deviation estimation result and the channel estimation result, the input signal is compensated, and the data is further determined to obtain the demodulation result.

As described above, the communication device (transmission device, reception device) of the present embodiment has a phase rotation sequence (C ₁ ) having periodicity in units of spreading factor and a phase rotation sequence that changes with a constant frequency width on the frequency axis. The spreading process is performed using (C ₂ ), and the despreading process is performed using the anti-phase rotation sequence (D ₁ , D ₂ ) having the opposite property to these phase rotation sequences. Also, it is assumed that a frame with a CP added is transmitted and received, and that the end of a slot (symbol block) is a known series, so that the CP portion is also a known series. As a result, in addition to the effects obtained in the first embodiment, slot (symbol clock) synchronization is performed based on the correlation between the known sequence corresponding to the CP not affected by the multipath delay wave and the received CP signal. Can be performed with high accuracy. Also, by using the symbol part of the known sequence at the end of the slot, frequency deviation estimation and channel estimation in the time domain are performed, and the input signal is compensated using these estimation results, so that a good demodulation result Can be obtained.

Embodiment 3 FIG.
In the present embodiment, the overall operation is the same as that of the communication apparatus of the second embodiment, but a communication apparatus in which the configuration of the communication apparatus on the receiving side is partially different will be described. That is, the configuration of the receiving device is different from that of the second embodiment. In this embodiment, a receiving device which is a part different from Embodiment 2 will be described.

FIG. 13 is a diagram illustrating a configuration example of a receiving apparatus according to the third embodiment. This receiving apparatus has a configuration in which the despreading processing unit 80a of the receiving apparatus (see FIG. 11) described in the second embodiment is replaced with a despreading processing unit 80b. The despreading processing unit 80b includes a combining unit 85 in place of the multiplier 81 and the correlator 82 of the despreading processing unit 80a, and the equalizer 84 is replaced with an equalizer 84b. The equalizer 84b performs equalization processing in the frequency domain and performs multiplication of the antiphase rotation sequence D ₂ (−θ) and the antiphase rotation sequence D ₁ (−φ _u ) in the frequency domain. The synthesizer 85 synthesizes in symbol units based on the spreading factor SF. Other components are the same as those of the receiving apparatus according to the second embodiment, and thus the same reference numerals are given and description thereof is omitted.

  FIG. 14 is a diagram illustrating a configuration example of the equalizer 84b. As illustrated, the equalizer 84b replaces the antiphase rotation sequence generation unit 849 of the equalizer 84 (see FIG. 12) described in Embodiment 2 with an antiphase rotation sequence generation unit 849b, and further includes a multiplier. 850 is added. Here, a different part from the equalizer 84 is demonstrated.

The inverse phase rotation sequence generation unit 849b generates a code sequence (inverse phase rotation sequence F (D ₁ · D ₂ )) for despreading for one slot in the frequency domain. Multiplier 850 multiplies the output from compensation unit 843 by the anti-phase rotation sequence F (D ₁ · D ₂ ) generated by anti-phase rotation sequence generation unit 849b in the frequency domain. Hereinafter, the detailed operation of the equalizer 84b will be described.

In the equalizer 84b, the anti-phase rotation sequence generation unit 849b applies the anti-phase rotation sequence D ₁ = C ₁ ^* (C ₁ is the multiplication of the transmission device) to the pilot sequence for one slot (corresponding to all “0” patterns). Phase rotation sequence multiplied by the device 21, * represents a complex conjugate) and D ₂ = C ₂ ^* (C ₂ represents a phase rotation sequence multiplied by the multiplier 22 of the transmission device, and * represents a complex conjugate). An inverse phase rotation sequence (F (D ₁ · D ₂ ), sequence length: N _sym × SF) is generated in advance by multiplication, conversion from the time domain to the frequency domain, and anti-phase rotation processing in the frequency domain. Save it. Further, this antiphase rotation sequence F (D ₁ · D ₂ ) is output to multipliers 848 and 850 as necessary.

The multiplier 850 multiplies the input signal from the compensation unit 843 by the anti-phase rotation sequence F (D ₁ · D ₂ ) output from the anti-phase rotation sequence 849b by one slot, and is used for spreading. Sample data (N _sym × SF) for one slot from which the code sequence is removed is extracted. The sample data is converted into a time domain signal by the IFFT unit 844 and then input to the synthesis unit 85 (see FIG. 13).

  Thus, in the receiving apparatus of the present embodiment, the phase rotation sequence used in the despreading process is prepared in advance in the frequency domain. This eliminates the need for FFT processing for calculating the phase rotation sequence, and allows the correlator to be changed to a synthesizer that synthesizes in units of spreading factor SF, thereby simplifying the circuit configuration.

Embodiment 4 FIG.
In the present embodiment, as in the second and third embodiments, a communication apparatus (transmitting apparatus, receiving apparatus) that performs transmission and reception with a CP added will be described. However, user (code) multiplexing, particularly assuming a downlink, is described. A communication device (transmission device) that realizes the function will be described.

  FIG. 15 is a diagram illustrating a configuration example of the transmission apparatus according to the fourth embodiment of the present invention. As illustrated, the transmission apparatus according to the present embodiment includes modulation sections 10-1 to 10-N, spread processing sections 20a-1 to 20a-N, a channel estimation slot generation section 24, and a channel estimation slot addition section 25. , An adder 26, a waveform shaping filter 30, a frequency conversion unit 40, and an amplifier 50. Spreading processing units 20 a-1 to 20 a -N have the same configuration, and include multipliers 21 and 22 and CP adding unit 23, respectively. The channel estimation slot generation unit 24 includes a multiplier 22 and a CP adding unit 23, which are the same as the multiplier 22 and the CP adding unit 23 included in the spreading processing units 20a-1 to 20a-N. Process.

  Modulating sections 10-1 to 10-N perform the same operation as modulating section 10 of the transmission apparatus described in the first embodiment, and spreading processing sections 20a-1 to 20a-N perform transmission described in the second embodiment. The same operation as the diffusion processing unit 20a of the apparatus is performed. The waveform shaping filter 30, the frequency conversion unit 40, and the amplifier 50 also perform the same operations as the waveform shaping filter 30, the frequency conversion unit 40, and the amplifier 50 of the transmission apparatus described in the first embodiment. In this embodiment, the description of the operation of the components already described in Embodiment 1 or 2 is omitted. That is, only operations of the channel estimation slot generation unit 24, the channel estimation slot addition unit 25, and the adder 26 will be described.

FIG. 16 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the fourth embodiment. This frame includes M (M is an arbitrary integer greater than or equal to 1) channel estimation slot and L (L is an arbitrary integer greater than or equal to 1) data slot common to each user (code), N data slots are multiplexed. Further, both the channel estimation slot and the data slot are configured by symbol blocks including N _sym + N _cp symbols, and have the same configuration as the slot (see FIG. 10) transmitted from the transmission apparatus according to the second embodiment. ing.

In the transmission apparatus of the present embodiment, each modulation unit (modulation units 10-1 to 10-N) and each diffusion processing unit (spreading processing units 20a-1 to 20a-N) arranged in the subsequent stage are implemented. The same processing as that of the modulation unit 10 and the spread processing unit 20 of the transmission apparatus described in the first embodiment is performed on the input signal. Specifically, each modulation unit modulates the input information sequence #u (u is a user number, u = 0 to N−1, N ≦ SF), and each spreading processing unit modulates the preceding stage modulation. After the input signal from the unit is sequentially multiplied by the phase rotation series C ₁ (φ _u ) and the phase rotation series C ₂ (θ), CP is added.

  Output signals from the respective spread processing units are input to an adder 26, and the adder 26 adds spread signals for N users (codes) input from the respective spread processing units.

The channel estimation slot generator 24 receives a pilot sequence whose pilot part is all 0 (corresponding to no modulation). In the channel estimation slot generator 24, the multiplier 22 applies C ₂ (θ) to the input signal. After multiplication, the CP adding unit 23 adds a CP to generate a channel estimation slot. This operation is obtained by excluding the process of multiplying the phase rotation sequence C ₁ (φ _u ) from the operation in the diffusion processing units 20a- ₁ to 20a-N (the process executed by the multiplier 21). The output of the channel estimation slot generator 24 has the property that the phase rotation sequence C ₂ (θ) changes in the frequency band Bw, and when there is no multipath delay wave, the frequency spectrum is flattened. can do. As a result, when performing channel estimation in the frequency domain, multipath delay waves can be accurately separated, and channel estimation accuracy can be improved. Here, not multiplying the phase rotation series C ₁ (φ _u ) is the same processing as when multiplying C ₁ (φ _u ) when the user number u = 0.

  The output from the channel estimation slot generation unit 24 (channel estimation slot) is input to the channel estimation slot addition unit 25 together with the output of the addition unit 26, and the channel estimation slot addition unit 25 receives from the adder 26. Using the data estimation slot and the channel estimation slot received from the channel estimation slot generator 24, a frame (see FIG. 16) in which M channel estimation slots are added in front of the L data slots. Generate. When multiplexing data slots for N users (codes), channel estimation accuracy can be improved by increasing the power of the channel estimation slots to the power corresponding to N slots.

  The output of the channel estimation slot adding unit 25 is input to the waveform shaping filter 30, and then transmitted from the antenna via the frequency converting unit 40 and the amplifier 50.

  As described above, in the transmission apparatus according to the present embodiment, on the downlink transmission side, spreading processing is performed using a phase rotation sequence having periodicity in units of spreading factor and a phase rotation sequence that changes with a constant frequency width on the frequency axis. It was decided to do. This makes it possible to multiplex while maintaining orthogonality between users.

  In addition, the amplitude characteristics of the channel estimation slot can be made flat in the frequency band. By increasing the power of the channel estimation slot by the number of multiplexed users, transmission with multipath delay waves is present. Channel estimation can be performed with high accuracy even under the influence of a road.

Embodiment 5 FIG.
In this embodiment, as in Embodiments 2 to 4, a communication apparatus (transmitting apparatus, receiving apparatus) that performs transmission and reception by adding a CP will be described. However, user (code) multiplexing, particularly assuming uplink A communication device (transmission device) that realizes the function will be described.

Note that the transmission / reception operation in the communication apparatus according to the present embodiment is basically the same as that of the communication apparatus described in the second embodiment, but it is assumed that uplink reception is performed in a communication system including a base station and a plurality of terminals. Only the transmission / reception operation (transmission / reception device configuration, frame configuration) when the transmission timing from each terminal differs according to the distance difference between the base station (reception side) and the terminal (transmission side) will be described. That is, in this embodiment, as shown in FIG. 17, it is assumed that uplink transmission is performed by each user (terminal). It is assumed that each reception timing is slightly shifted on the base station side (reception side) due to a difference in distance from the base station. FIG. 17 is a diagram illustrating a configuration example of a terminal (transmission apparatus) on the transmission side in the communication system according to the fifth embodiment. The configuration and operation of each terminal (transmission device) shown in FIG. 17 are the same as those of the transmission device (see FIG. 9) described in the second embodiment. However, the spread processing unit 20a of each transmitter uses different phase rotation sequences C ₁ (φ _u (j)) for user identification. u is a user number (u = 0 to N−1, N ≦ SF), and j is a chip number for each symbol (j = 0 to SF−1).

FIG. 18 is a diagram illustrating a configuration of a frame transmitted and received by the communication apparatus according to the fifth embodiment. This frame includes M (M is an arbitrary integer greater than or equal to 1) channel estimation slots and L (L Is an arbitrary integer greater than or equal to 1). Further, as shown in the figure, both the channel estimation slot and the data slot included in the frame are configured by symbol blocks including N _sym + 2 · N _cp symbols. Here, N _cp is the number of symbols in the CP portion, SF is the spreading factor in DS-CDMA, N _sym is the number of symbols in the frequency domain conversion target portion, N _d is the number of data symbols, and N _k is the number of symbols in the known sequence portion. is there. As shown in FIG. 18, when N _k ≧ N _cp , the symbol of the CP portion can also be a completely known symbol. At this time, if the pilot symbol start / end portion and the known sequence portion are exactly the same, the reception side can perform correlation processing using a sequence of the CP portion prepared in advance. As a result, the synchronization timing can be estimated without being affected by the multipath delayed wave. Further, as shown in the first embodiment, if the pilot symbol part sequence is an all-zero pattern (corresponding to no modulation), it depends on the properties of the two phase rotation sequences C ₁ and C _2. Even when the pilot symbols are spread, the amplitude characteristics on the frequency band can be made flat, and channel estimation can be performed with high accuracy even when multipath delay waves are present. Note that the CP part is arranged at the beginning and end of each slot, assuming that each user (terminal) performs uplink transmission, and the position of the terminal differs among users (terminals). Therefore, when the difference in distance from the base station is different and the reception timing on the base station receiving side is slightly shifted back and forth, it is absorbed by the CP portion to maintain orthogonality between users. .

  FIG. 19 is a diagram illustrating a configuration example of a receiving-side communication device (receiving device) according to the fifth embodiment. As illustrated, the receiving apparatus according to the present embodiment includes a frequency conversion unit 60, a waveform shaping filter 70, a CP removal unit 83, despreading processing units 80d-1 to 80d-N, and demodulation units 90-1 to 90-N. Is provided. The frequency conversion unit 60 and the waveform shaping filter 70 are the same as the frequency conversion unit 60 and the waveform shaping filter 70 included in the receiving apparatus (see FIG. 11) described in the second embodiment. The despreading processing units 80d-1 to 80d-N have the same configuration, and include a multiplier 81, a correlator 82, and an equalizer 84d. Note that the multiplier 81 and the correlator 82 of each despreading unit perform the same processing as the multiplier 81 and the correlator 82 included in the receiving apparatus described in the second embodiment. However, each correlator 82 uses a different antiphase rotation sequence. The CP removing unit 83 is the same as the CP removing unit 83 included in the receiving apparatus described in the second embodiment. Demodulator 90-1 to 90-N performs the same processing as demodulator 90 provided in the receiving apparatus described in the second embodiment.

  FIG. 20 is a diagram illustrating a configuration example of the equalizer 84d of each despreading processing unit. As illustrated, the equalizer 84d replaces the anti-phase rotation sequence generation unit 849 of the equalizer 84 (see FIG. 12) described in Embodiment 2 with an anti-phase rotation sequence generation unit 849b, and further, an IFFT unit. 851, a time domain mask processing unit 852, and an FFT unit 853 are added. Note that the anti-phase rotation sequence generation unit 849b is the same as the anti-phase rotation sequence generation unit 849b included in the equalizer 84b (see FIG. 14) described in the third embodiment. Here, a different part from the equalizer 84 or 84b demonstrated in Embodiment 2 or 3 is demonstrated. The IFFT unit 851, the time domain mask processing unit 852, and the FFT unit 853 constitute channel estimation result extraction means.

  As an example, the operation of the equalizer 84d for the 0th user (u = 0) will be described. When receiving the signal from the multiplier 848, the IFFT unit 851 of the equalizer 84d converts the signal into a time domain signal. The time domain channel estimation result, which is output from the IFFT unit 851, is input to the time domain mask processing unit 852.

Here, the channel estimation result (user number: # 0) input to the time domain mask processing unit 852 is affected by the multipath delay wave, and for example, the time as shown in FIG. It has a waveform. In FIG. 21A, the time domain sample is expressed by 0 to N _sym · SF-1 and depends on the phase rotation amount of D ₁ (φ _u ) due to the cyclic nature of the antiphase rotation series D ₁ · D ₂ . The channel estimation results for the spreading factor SF can be seen at the same time. Since the multiplier 848 in this example performs multiplication processing of the anti-phase rotation sequence (F (D ₁ · D ₂ ), sequence length: N _sym × SF) for the user number # 0, the target 0th The channel estimation results of the users of 0 to N _sym appear. Channel estimation results appearing in other time regions (N _{sym to} N _sym · SF) are channel estimation results for users other than user # 0. For this reason, the channel estimation results of the other users # 1 to N (≦ SF) are not necessary for the equalization (compensation) process by the user # 0, and thus need to be masked. Therefore, the time domain mask processing unit 852 performs mask processing on the channel estimation results other than the target user (user # 0) among the input channel estimation results, and as illustrated in FIG. The channel estimation result of # 0 is extracted and output to the FFT unit 853. The FFT unit 853 converts the input signal into a frequency domain signal and outputs it to the compensation unit 843.

  Although the operation for the 0th user has been described as an example, the operation of the equalizer 84d for users other than the 0th user is the same.

  In the demodulating units 90-1 to 90-N, when there is an input from the correlator 82 in the previous stage, the estimation of the frequency deviation in the time domain and the channel are performed using the known sequence symbol parts at the head and tail in the frame. Estimation is performed, and based on each obtained estimation result, compensation of the input signal and data determination are performed, and a demodulation result is obtained.

As described above, the communication device (transmission device, reception device) of the present embodiment has a phase rotation sequence (C ₁ ) having periodicity in units of spreading factor and a phase rotation sequence that changes with a constant frequency width on the frequency axis. The spreading process is performed using (C ₂ ), and the despreading process is performed using the anti-phase rotation sequence (D ₁ , D ₂ ) having the opposite property to these phase rotation sequences. Furthermore, the transmission / reception of a frame with a CP added to the beginning and end is performed, and the beginning and end of a slot (symbol block) are set as known series, so that each CP portion is also set as a known series. Thereby, since the channel estimation result for each user can be separated in the time domain while maintaining orthogonality between users, channel estimation for each user can be performed even when a multipath delayed wave exists. In addition, slot (symbol clock) synchronization can be performed with high accuracy by the correlation between a known sequence corresponding to a CP that is not affected by a multipath delay wave and the received CP signal. Furthermore, using the known sequences before and after the slot, frequency deviation estimation and channel estimation are performed in the time domain, and the input signal is compensated using these estimation results to obtain a good demodulation result. be able to.

  Further, the constellation of the signal after spreading processing basically rotates on the unit circumference, so that the frequency of passing through the origin can be suppressed, and the power efficiency can be improved in the amplifier of the transmission apparatus.

  As described above, the transmission apparatus according to the present invention is useful for a DS-CDMA communication system, and particularly for realizing communication with flat amplitude characteristics in the frequency band while maintaining orthogonality between users. Is suitable.

  10, 10-1 to 10-N modulation unit, 20, 20a, 20a-1 to 20a-N spreading processing unit, 21, 22, 81, 845, 846, 848, 850 multiplier, 23 CP addition unit, 24 channels Estimating slot generation unit, 25 channel estimation slot adding unit, 26 adder, 30, 70 waveform shaping filter, 40, 60 frequency converting unit, 50 amplifier, 80, 80a, 80b, 80d-1 to 80d-N despreading Processing unit, 82 correlator, 83 CP removal unit, 84, 84b, 84d equalizer, 85 synthesis unit, 841 Nyquist point extraction unit, 842, 847, 853 FFT unit, 843 compensation unit, 844, 851 IFFT unit, 849 , 849b Anti-phase rotation sequence generation unit, 852 time domain mask processing unit, 90, 90-1 to 90-N demodulation unit.

Claims (2)

A transmission apparatus constituting a communication apparatus on the transmission side of a DS-CDMA communication system,
Modulation means for performing modulation processing on information to be transmitted;
Spreading means for spreading the signal modulated by the modulation means using a phase rotation sequence having periodicity in units of spreading factor;
Frequency conversion means for performing frequency conversion on the signal spread by the spreading means;
A transmission device comprising: A transmission apparatus constituting a communication apparatus on the transmission side of a DS-CDMA communication system,
Modulation means for performing modulation processing on information to be transmitted;
First spreading means for spreading the signal modulated by the modulating means using a phase rotation sequence having periodicity in spreading factor units;
Second spreading means for spreading the signal spread by the first spreading means by using a phase rotation sequence that changes the frequency on the frequency axis;
Frequency conversion means for performing frequency conversion on the signal spread by the second spreading means;
A transmission device comprising:

Images