JP2006325099A - Cdma transmitting device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the need of channel estimation, to eliminate the need of a pilot signal and to prevent a transmission data rate from dropping. <P>SOLUTION: A transmitting side differentially encodes a transmission signal such as a DS-CDMA signal by a frequency domain, adds a guard interval and transmits the transmission signal with the guard interval added thereto. In a receiving side, a G eliminating part 42 eliminates a guard interval of a chip sequence from a receiving part 41 to obtain the chip sequence. An FFT (fast Fourier transform) part 401 breaks down each chip block for each N<SB>c</SB>chip into N<SB>c</SB>orthogonal frequency components by N<SB>c</SB>-point FFT. A differential decoding part 43 differentially decoding each frequency component. An equalizing part 404 equalizes each frequency component. An adding part 405 adds the N<SB>c</SB>frequency components from the equalizing part 404 to restore a data sequence. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a CDMA transmission apparatus and method, and more particularly, to a CDMA transmission apparatus and method using frequency domain differential coding and decoding in a direct spreading code division multiple access (DS-CDMA) system.

  In the third generation mobile communication system, direct spreading code division multiple access (DS-CDMA) is used. In DS-CDMA, transmission data is transmitted with a spectrum spread using a higher-speed spreading code. On the receiving side, the transmission data is restored by multiplying the received signal by the same spreading code as the spreading code used for transmission and integrating (correlation calculation). By the way, it is known that the mobile communication channel is a frequency selective channel composed of a number of paths having different delay times. The number of passes is about 3-4. In DS-CDMA, excellent transmission characteristics can be obtained by a Rake receiver that separates and combines signals received by propagating through each path by a correlator (also referred to as a Rake finger) corresponding to the number of paths. The third generation mobile communication system aims at data transmission up to about 10 Mbps. However, the next generation mobile communication aims at ultra-high speed transmission of 100 Mbps or more. In such an ultra-high speed transmission, the number of paths becomes a considerable number, and the frequency selectivity becomes considerably strong. In this case, the number of correlators of the Rake receiver increases and becomes complicated. If the number of correlators is set to a certain number, the received signal power of all paths cannot be collected and the transmission characteristics may deteriorate.

Therefore, recently, frequency domain equalization (FDE), which replaces the Rake receiver, has appeared (Non-Patent Document 1). A frequency selective channel means that the transfer function of the channel is not constant but varies in the signal frequency band. The spectrum of a signal received through such a channel is distorted. Therefore, in FDE, the received signal spectrum is obtained by decomposing the received signal into N _c orthogonal frequency components by N _c -point fast Fourier transform (FFT) and multiplying the received signal spectrum by an equalization weight close to the inverse of the channel transfer function. To compensate for distortion. In such an FDE, the channel transfer function must be estimated. This is called channel estimation. For this purpose, there is a method of periodically transmitting a pilot signal of a base on the receiving side and receiving it to perform channel estimation (Non-Patent Document 2).

F. Adachi, T .; Sao, and T.K. Itagaki, “Performance of multicode DS-CDMA using frequency domain equalization in a frequency selective fading channel,” IE Electroelectronics. 39, no. 2, pp. 239-241, Jan. 2003. Kazuaki Takeda, Fumiyuki Adachi, “Error rate performance of DS-CDMA frequency domain equalization using pilot channel estimation,” IEICE Technical Report, RCS 2004-86, pp. 61-65, June 2004.

In mobile communications, mobile terminals generally move at high speed. At this time, the channel transfer function varies with time. In order to estimate such a time-varying channel transfer function with high accuracy, it is necessary to shorten the transmission period of the pilot signal. That is, the pilot transmission rate must be increased. That is, conventionally, there has been a problem that the transmission data rate is reduced. If there is a method that does not require channel estimation, DS-CDMA signal transmission that can cope with high-speed movement without the need to transmit a pilot signal becomes possible. However, no such transmission method has been proposed so far.
In view of the above points, the present invention aims to solve the following problems.
(1) Make channel estimation unnecessary.
(2) The pilot signal is not required and the transmission data rate is not reduced.
(3) To achieve a high-quality transmission by obtaining a frequency diversity effect by performing frequency domain equalization in the frequency domain decoding process on the receiving side.

In the present invention, on the transmission side, a transmission signal such as a DS-CDMA signal is differentially encoded in the frequency domain and transmitted with a guard interval added. In particular, in one embodiment of the present invention, an FFT (Fast Fourier Transform) is used to decompose a transmission DS-CDMA signal into orthogonal frequency components, differentially encode each frequency component, and then IFFT. (Inverse fast Fourier transform, inverse fast Fourier transform) is used to generate a frequency-domain differentially encoded DS-CDMA signal and transmit it with a guard interval added.
On the receiving side, channel estimation is unnecessary because it is only necessary to perform differential decoding after decomposing the received signal into orthogonal frequency components using FFT. First, the guard interval is deleted from the received signal, the frequency domain differentially encoded DS-CDMA signal received using FFT is decomposed into orthogonal frequency components, and each frequency component is differentially decoded and added. The received data symbol is obtained by determining the symbol. In another embodiment, after each frequency component is differentially decoded, a DS-CDMA signal is reproduced using IFFT, despread and symbol determination is performed to obtain received data symbols.

According to the first solution of the present invention,
In a CDMA transmission apparatus comprising a transmitter and a receiver,
The transmitter is
A data modulation unit that obtains a data symbol sequence by performing data modulation on a transmission data sequence;
A differential encoding unit that differentially encodes a data symbol sequence to obtain a differentially encoded data symbol sequence;
A spreading unit that obtains a chip block consisting of N _c chips (N _c is the number of FFT points) by multiplying a differentially encoded data symbol sequence from the differential encoding unit by a spreading code;
An additional unit that copies a predetermined chip at the end of each chip block from the spreading unit and adds it to the head of the block as a guard interval;
A transmitting unit for transmitting a chip block sequence to which a guard interval from the adding unit is added;
With
The receiver
Receiving a chip block sequence from the transmission unit, sampling a received signal for each chip time to obtain a chip sequence; and
A deletion unit that divides the chip series from the reception unit into chip blocks for each _Nc chip and deletes the guard interval from each chip block;
An FFT unit that decomposes the chip series of each chip block from the deletion unit into N _c orthogonal frequency components by N _c -point FFT;
N _c pieces of provided for each orthogonal frequency components, and N _c pieces of differential decoder for differentially decoding the respective frequency components from the FFT unit,
N _c pieces of provided for each orthogonal frequency components, the output from the differential decoder, the N _c pieces of equalizer that performs equalization for each frequency component,
An adder for adding N _c frequency components from each of the equalization units;
There is provided a CDMA transmission apparatus including a symbol determination unit that obtains a reception data symbol corresponding to a transmission data symbol.

According to the second solution of the present invention,
For each m-th chip block, a transmission data symbol sequence {a _{m, n} ; n = 0 to (N _c / N _c ) consisting of N _c / SF symbols (N _c is the number of FFT points and SF is a spreading factor). SF) -1} multiplied by the spreading code c _m (t);
An FFT unit for decomposing the m-th chip block composed of N _c chips obtained by the spreading unit into N _c orthogonal frequency components by N _c -point FFT;
N _c pieces of provided for each frequency component, and N _c pieces of differential encoding portion for obtaining a differential coding the frequency components of each frequency component by differential coding,
The N _c pieces of differential coding the frequency components from the differential encoding unit, N c _- and IFFT unit obtaining a time domain signal of the chip blocks by applying the point IFFT consisting N _c chips,
An additional unit that copies a predetermined amount of chips at the end of the time domain signal of the chip block consisting of _Nc chips from the IFFT unit and adds it to the head of each chip block as a guard interval;
A transmitting unit for transmitting a chip block sequence to which a guard interval from the adding unit is added;
A CDMA transmission apparatus on the transmission side comprising:

According to the third solution of the present invention,
A receiving unit that samples the received signal for each chip time and obtains a chip sequence of the received frequency domain differentially encoded signal;
A deletion unit that divides the chip series from the reception unit into chip blocks for each N _c chip (N _c is the number of FFT points), and deletes a guard interval from each chip block;
An FFT unit that decomposes the chip series of each chip block from the deletion unit into N _c orthogonal frequency components by N _c -point FFT;
N _c pieces of provided for each orthogonal frequency components, and N _c pieces of differential decoder for differentially decoding the respective frequency components from the FFT unit,
N _c pieces of provided for each orthogonal frequency components, the output from the differential decoder, the N _c pieces of equalization unit that performs frequency domain equalization for each frequency component,
An IFFT unit obtaining a time domain signal of _{N c} chip by applying the point IFFT, - _{N c} to _{N c} number of frequency components from the equalization unit
A despreading unit that despreads the output of the IFFT unit with a spreading code;
An integration unit that integrates the output of the despreading unit for each number of chips per data symbol;
There is provided a CDMA transmission apparatus on the receiving side provided with a symbol determination unit that obtains a reception data symbol corresponding to transmission data symbols am _{, n} .

According to the fourth solution of the present invention,
A transmission side CDMA transmission apparatus as described above;
There is provided a CDMA transmission apparatus including the above-described receiving-side CDMA transmission apparatus.

According to the fifth solution of the present invention,
On the sending side,
The transmission data sequence is data modulated to obtain a data symbol sequence,
Differential encoding the data symbol sequence to obtain a differential encoded data symbol sequence,
Multiplying the differentially encoded data symbol sequence by a spreading code to obtain a chip block consisting of N _c chips (N _c is the number of FFT points),
Copy the specified chip at the end of each chip block and add it to the beginning of that block as a guard interval,
Send chip block sequence with guard interval added,
On the other hand, on the receiving side,
Receiving the chip block sequence from the transmitting side, sampling the received signal every chip time to obtain a chip sequence,
Dividing the chip series into chip blocks for each _Nc chip, and removing the guard interval from each chip block;
The chip sequence for each chip block which the guard interval has been deleted N _c - decomposed into N _c pieces of orthogonal frequency components by the point FFT,
For each of the N _c orthogonal frequency components, each frequency component is differentially decoded,
For each of the _Nc orthogonal frequency components, the differentially decoded output is equalized for each frequency component;
Add each equalized _Nc frequency components,
A CDMA transmission method is provided for obtaining received data symbols corresponding to transmitted data symbols.

According to the sixth solution of the present invention,
For each m-th chip block, a transmission data symbol sequence {a _{m, n} ; n = 0 to (N _c / N _c ) consisting of N _c / SF symbols (N _c is the number of FFT points and SF is a spreading factor). SF) −1} is multiplied by the spreading code c _m (t),
The resulting N _c consisting chips m th chip block N _c - decomposed into N _c pieces of orthogonal frequency components by the point FFT,
For each of the _Nc frequency components, each frequency component is differentially encoded to obtain a differentially encoded frequency component,
The N _c pieces of differential coding the frequency components, N c _- to obtain a time domain signal of the chip block of N _c chip by applying the point IFFT,
A portion of the time domain signal at the end of the chip block consisting of _Nc chips is copied and added as a guard interval to the beginning of each chip block,
A transmitting-side CDMA transmission method for transmitting a chip block sequence to which a guard interval is added is provided.

According to a seventh solution of the present invention,
The received signal is sampled at every chip time to obtain a chip sequence of the received frequency domain differentially encoded signal,
The chip series is divided into chip blocks every N _c chips (N _c is the number of FFT points), and the guard interval is deleted from each chip block,
The chip sequence for each said chip block N _c - decomposed into N _c pieces of orthogonal frequency components by the point FFT,
For each of the _Nc orthogonal frequency components, differentially decode each frequency component;
Perform frequency domain equalization for each frequency component on the differentially decoded output for each of N _c orthogonal frequency components,
To obtain a time domain signal of N _c chip by applying the point IFFT, - the equalized N _c number of frequency components N _c
The IFFT output is despread with a spreading code,
For the despread output, integrate for each number of chips per data symbol,
A receiving side CDMA transmission method for obtaining received data symbols corresponding to transmitted data symbols am _{, n} is provided.

According to the eighth solution of the present invention,
A transmission side CDMA transmission method as described above;
There is provided a CDMA transmission method including the above-described CDMA transmission method on the receiving side.

According to the present invention, there are mainly the following specific effects.
(1) Channel estimation can be made unnecessary.
(2) Since a pilot signal is unnecessary, the transmission data rate is not reduced.
(3) Since frequency domain equalization is performed in the frequency domain decoding process on the reception side, a high quality transmission can be realized because a frequency diversity effect is obtained.

1. First Embodiment (1) Transmission Side FIG. 1 is a configuration diagram of a transmitter according to a first embodiment. FIG. 2 is an explanatory diagram of data processing on the transmission side. In the first embodiment, a case where the spreading factor (SF) is equal to the number of FFT points (N _c ) (that is, SF = N _c ) will be described. In addition, the value of the parameter in FIG. 2 shows an example, and is not limited to this.
In the transmitter, first, the data modulation unit 31 modulates transmission data by an appropriate modulation scheme such as QPSK, FSK, QAM, and the like, and transmits a transmission data symbol sequence {a _m ; m = 0, 1, 2,. And The differential encoding unit 32 differentially encodes the transmission data symbol sequence {a _m ; m = 0, 1, 2,... {B _m ; m = 0, 1, 2,. Therefore, the differential encoding unit 32 includes a multiplier 301 and a one symbol delay unit 302.

b _m = a _m b _m−1 (4)

The spreading unit 33 multiplies the data symbol b _m by the spreading code c _m (t) to generate a chip sequence s _m (t) = b _m c _m (t) composed of N _c chips constituting the m-th chip block. Get. Here, T is a data symbol length, a chip length is T _c , a transmission data rate is 1 / T, and a spreading code rate (referred to as a chip rate) is 1 / T _c . One transmission data is converted into T / _Tc chips. T / _Tc is called the spreading factor (SF). Therefore, the chip rate is SF times the symbol rate. The case where the spreading factor (SF, the number of chips in one bit) is equal to the number of FFT points (N _c ) is T = N _c T _c . The guard interval (GI) adding unit 34 copies the last _Ng chips of each chip block and adds it as a guard interval to the head of the block, and the chip series s of the mth chip block to which this guard interval is added. _m (t) is transmitted (see Non-Patent Document 1). By adding this guard interval, the length of the chip block becomes N _c + N _g chips. Therefore, the GI adding unit 34 further compresses the time length of the chip block to which the guard interval is added to the time length of the chip block before the guard interval is added in order not to reduce the transmission symbol rate. As a result, the chip rate becomes SF × (1 + N _g / N _c ) times the symbol rate. The transmitter 35 transmits the chip block sequence to which the guard interval is added in this way. The reason why the guard interval needs to be added is that a signal received by propagating through a channel having a plurality of paths having different delay times is decomposed into frequency components by applying FFT and differentially decoded. is there.
As described above, in the first embodiment, instead of the frequency domain differential encoding, the well-known differential encoding for each symbol is applied, and therefore FFT and IFFT are not required. Is one of the features.

(2) Receiving Side FIG. 3 is a configuration diagram of the first embodiment of the receiver.
In the receiver, first, the receiving unit 41 samples the received signal from the transmitter for each chip time. In this way, the received differentially encoded DS-CDMA signal chip sequence is obtained. Next, the GI deletion unit 42 divides the chip series into chip blocks for each N _c + N _g chip. Since a _Ng chip guard interval is added to each chip block, the GI deletion unit 42 deletes the guard interval from the mth chip block to obtain a chip sequence r _m (t) of N _c chips. FFT unit 401, a chip sequence _r m (t), as in the following equation, _{N c} - exploded orthogonal frequency components of the _{N c} pieces by the point _{FFT R m (k), k} = 0~N c -1, the To do.

The differential decoding unit 43 is provided for each orthogonal frequency component, and differentially decodes each frequency component. Therefore, the differential decoding unit 43 includes a one-block delay unit 402 and a multiplier 403. Next, the equalization unit 404 equalizes the output of the differential decoding unit 43 for each frequency component to obtain frequency components S _m (k), k = 0 to N _c −1. . Thus, in differential decoding, since the transmission function of the channel is not constant, the transmission spectrum is distorted, so that frequency domain equalization is also performed simultaneously. (Note that “^”, “ ^˜ ”, etc. are appended above the reference numerals as shown in the figure / formula, but are added next to the reference numerals in this specification for the convenience of application procedures. .)
In differential decoding and equalization of the kth (k = 0 to N _c −1) frequency component, the orthogonal frequency component R _m (k) of the current chip block and the previous chip block by the one-block delay unit 402 are used. Is used to perform differential decoding and equalization as follows using the orthogonal frequency component R _m−1 (k).
_{S ^ m (k) = w} m (k) R m (k) R * m-1 (k) (5)
Here, * is a complex conjugate, and w _m (k) is an equalization weight. The equalization unit 404 can create the equalization weight w _m (k) using either ZF (zero forcing) or MMSE (minimum mean square error), for example, as shown in the following equation.

ここで、Ｃ_ｍ（ｋ）は拡散符号ｃ_ｍ（ｔ）のｋ番目の周波数の成分である。受信側で拡散符号ｃ_ｍ（ｔ）を予め知っているから、Ｃ_ｍ（ｋ）を計算できる。σ^２は雑音電力である。

Here, C _m (k) is a component of the k-th frequency of the spread code c _m (t). Since the receiving side knows the spreading code c _m (t) in advance, C _m (k) can be calculated. σ ² is noise power.

FIG. 4 shows a configuration diagram for noise power measurement in MMSE. The noise power is obtained by, for example, measuring the power when there is no signal by providing a measurement unit 45 that measures the output signal for each frequency component of the FFT unit 401 (or the FFT unit 23 described later). be able to.
Next, the addition unit (Σ unit) 405 adds the frequency components S _m (k) and k = 0 to N _c −1 as in the following equation to obtain a soft decision value a _m .

Next, the symbol determination unit 44 performs symbol determination to obtain received data symbols a ^to _m . For example, in the case of two-phase phase modulation, it can be determined as positive or negative.
This reception method is characterized in that differential decoding, equalization, and despreading are collectively performed in the frequency domain, so that IFFT and a despreader are not required. One feature of this embodiment is that no channel estimation is required.

2. Second Embodiment (1) Transmission Side FIG. 5 shows a configuration diagram of a transmitter according to a second embodiment. FIG. 6 is an explanatory diagram of data processing on the transmission side. In the second embodiment, SF < _Nc .
On the transmission side, the spreading unit 11 spreads the N _c / SF transmission data symbol sequences {a _{m, n} ; n = 0 to (N _c / SF) −1} transmitted in the m th chip block. Multiply by c _m (t) to obtain the chip sequence A _m (t) of the m th chip block. That is, A _m (t) = a _{m, n} × c _m (t), t = 0 to N _c −1. Here, n is an integer part of t / SF, and n = 0 to ( _Nc / SF) -1. That is, the number of transmission data symbols included in each chip block is N _c / SF. Note that, similarly to the first embodiment, a data modulation unit that modulates transmission data by an appropriate modulation scheme such as QPSK, FSK, and QAM to form a transmission data symbol sequence may be provided before the spreading unit 11. Good. The FFT unit 12 decomposes the chip sequence A _m (t) of the m-th chip block into N _c orthogonal frequency components S _m (k), k = 0 to N _c −1 by N _c -point FFT. . In order to perform the FFT, a serial / parallel converter may be provided in the preceding stage separately from the FFT unit 12.

Next, the frequency domain differential encoding unit 13 differentially encodes each frequency component.
FIG. 7 is a configuration diagram of the frequency domain differential encoding unit on the transmission side.
Each frequency domain differential encoding unit 13 includes a divider 101, a one-block delay unit 102, and a normalization unit 103. In the differential encoding unit 13 of the k-th (k = 0 to N _c −1) frequency component, the k-th frequency component obtained by differential encoding of the immediately preceding chip block by the one-block delay unit 102. T _m−1 (k) is obtained, and the normalization unit 103 further normalizes the amplitude of the kth frequency component. Then, the divider 101 divides the orthogonal frequency component S _m (k) of the current chip block by the output of the normalization unit 103 to perform differential encoding as follows.
_Tm (k) = _Sm (k) / { _Tm-1 (k) / | _Tm-1 (k) |} (1)
Here, | z | represents the absolute value of the complex number z.
Then, IFFT unit 14, differential coding the frequency components _{T m (k), k =} 0~N c -1, the _{N c} - a time domain signal by applying a point _{IFFT s m (t), t} = 0 to N _c −1 are obtained. This signal is a chip sequence of the m-th chip block of the frequency domain differentially encoded DS-CDMA signal. Such processing is applied to each block to obtain a chip sequence s _m (t) of the m-th chip block subjected to frequency domain differential encoding. Here, s _m (t) is expressed by the following equation.

Next, before transmitting, the GI adding unit 15 copies and adds the last _Ng chips of each chip block to the head of each block (see Non-Patent Document 1). This added _Ng chip is called a guard interval. The reason why the guard interval needs to be added is that a signal received by propagating through a channel having a plurality of paths having different delay times is decomposed into frequency components by applying FFT and differentially decoded. is there. Due to the addition of the guard interval, the length of each chip block becomes N _c + N _g chips. Therefore, the GI addition unit 15 further compresses the time length of the chip block to which the guard interval is added to the time length of the chip block before the addition of the guard interval so as not to reduce the transmission symbol rate. As a result, the chip rate becomes SF × (1 + N _g / N _c ) times the symbol rate. The transmission unit 16 transmits a chip block sequence to which a guard interval is added.

(2) Receiving Side FIG. 8 shows a configuration diagram of a second embodiment of the receiver.
On the receiving side, the receiving unit 21 samples the received signal for each chip time. In this way, the received frequency domain differentially encoded DS-CDMA signal chip sequence is obtained. Next, the GI deletion unit 22 divides the chip series into chip blocks for each N _c + N _g chip. Since a _Ng chip guard interval is added to each chip block, the _Nc chip chip sequence r _m (t) is obtained by deleting the guard interval from the m th chip block. The FFT unit 23 converts the chip sequence r _m (t) (the number of transmission data included in the chip block is N _c / SF) to N _c orthogonal frequency components R _m (k) by N _c -point FFT, Decomposes into k = 0 to N _c −1.
Next, each frequency component is differentially decoded by the frequency domain differential decoding unit 24, and further, frequency domain equalization is performed by the equalization unit 25, so that the frequency components S _m (k), k = 0 to N _c − 1. Here, in the differential decoding, since the transmission function of the channel is not constant and the transmission spectrum is distorted, frequency domain equalization is also performed at the same time. One feature of this embodiment is that no channel estimation is required. (Note that “^”, “ ^˜ ”, etc. are appended above the reference numerals as shown in the figure / formula, but are added next to the reference numerals in this specification for the convenience of application procedures. .)
Then, IFFT unit _{26, S ^ m (k),} k = 0~N c -1, the _{N c} - a time domain signal by applying a point _{^{IFFT A ~ m (t),}} t = 0~N c - 1. Here, A ^to _m (t) are as follows.

Next, in the despreading unit 27, the output of the IFFT unit 26 is despread, and in the integrating unit 28, the soft decision _values a ^ _{m, n} are obtained by integration for each SF chip according to the following equation. The determination unit 29 performs symbol determination to restore the received data symbols a ^to _{m, n} (n = 0 to (Nc / SF) -1). Note that a symbol determination unit that performs symbol determination and restores a transmission data symbol may be provided in the subsequent stage of the integration unit 25 as in the first embodiment.

FIG. 9 is a configuration diagram of the frequency domain differential decoding unit and equalization unit on the receiving side. In the differential decoding unit 24 for the k-th (k = 0 to N _c −1) frequency component, the 1-block delay unit 201 and the multiplier 202 cause the orthogonal frequency component R _m (k) of the current chip block and the previous one. Differential decoding is performed using the orthogonal frequency component R _m−1 (k) of the chip block, and further, frequency domain equalization is performed by the equalization unit 25, thereby decoding as follows.

_{S ^ m (k) = w} m (k) R m (k) R * m-1 (k) (2)

Here, * is a complex conjugate, and w _m (k) is an equalization weight.
The equalization unit 25 can create w _m (k) using either ZF (zero forcing) or MMSE (minimum mean square error), for example, as shown in the following equation.

Here, σ ² is noise power. This method can be obtained by measuring the noise power of each frequency component of the FFT unit 23 as in the first embodiment. That is, as shown in the configuration diagram for noise power measurement in MMSE in FIG. 4, noise power is measured by, for example, providing a measurement unit 45 that measures an output signal for each frequency component of the FFT unit 401. It can be obtained by measuring the power when there is no signal.
FIG. 10 shows a configuration diagram of the equalization weight creating unit.
The equalization weight creating unit 30 uses the 1-block delay unit 251, for example, from the output of the symbol determination unit 29, to determine a data symbol sequence consisting of N _c / SF data symbols for which the symbol of the previous chip block has been determined { _{^{a ~ m-1, n:}} n = 0~ (n c / SF) obtained -1}, the data symbol sequence ^a _{~ m-1, n} spread code _{c m-1} (t) by the spreading section 252 Spread with. After that, the FFT unit 253 performs N _c -point FFT on the time domain signals A ^to _m−1 (t) from the spreading unit 252 to obtain k _- th frequency components S ^to _m−1 (k). In the equalization weight calculation unit 254 provided for each of the N _c frequencies, the equalization weight w is calculated using the equation (3) according to ZF or MMSE determined in advance based on S ^to _m−1 (k). _m (k) is obtained and given to the multipliers of the respective spreading units 25, and the multipliers multiply the input data by the equalization weights w _m (k).

  The present invention may be a candidate for an uplink transmission method for next-generation wireless communication.

The block diagram of 1st Embodiment of a transmitter. Explanatory drawing of the data processing of the transmission side. The block diagram of 1st Embodiment of a receiver. The block diagram for the noise power measurement in MMSE. The block diagram of 2nd Embodiment of a transmitter. Explanatory drawing of the data processing of the transmission side. The block diagram of the frequency domain differential encoding part by the side of a transmission. The block diagram of 2nd Embodiment of a receiver. The block diagram of the frequency domain differential decoding part and equalization part of a receiving side. The block diagram of an equalization weight preparation part.

Explanation of symbols

31 Data Modulation Unit 32 Differential Encoding Unit 33 Spreading Unit 34 Guard Interval (GI) Addition Unit 35 Transmission Unit 301 Multiplier 302 1 Symbol Delay Unit 41 Reception Unit 42 GI Deletion Unit 43 Differential Decoding Unit 44 Symbol Determination Unit 401 FFT Unit 402 1 block delay unit 403 multiplier 404 equalization unit 405 addition unit (Σ unit)
DESCRIPTION OF SYMBOLS 11 Spreading part 12 FFT part 13 Frequency domain differential encoding part 14 IFFT part 15 GI addition part 16 Transmission part 101 Divider 102 1 block delay part 103 Normalization part 21 Reception part 22 GI deletion part 23 FFT part 24 Frequency domain difference Dynamic decoding unit 25 Equalization unit 26 IFFT unit 27 Despreading unit 28 Integration unit 29 Symbol determination unit 201 1 block delay unit 202 Multiplier 30 Equalization weight generation unit

Claims (17)

In a CDMA transmission apparatus comprising a transmitter and a receiver,
The transmitter is
A data modulation unit that obtains a data symbol sequence by performing data modulation on a transmission data sequence;
A differential encoding unit that differentially encodes a data symbol sequence to obtain a differentially encoded data symbol sequence;
A spreading unit that obtains a chip block consisting of N _c chips (N _c is the number of FFT points) by multiplying a differentially encoded data symbol sequence from the differential encoding unit by a spreading code;
An additional unit that copies a predetermined chip at the end of each chip block from the spreading unit and adds it to the head of the block as a guard interval;
A transmitting unit for transmitting a chip block sequence to which a guard interval from the adding unit is added;
With
The receiver
Receiving a chip block sequence from the transmission unit, sampling a received signal for each chip time to obtain a chip sequence; and
A deletion unit that divides the chip series from the reception unit into chip blocks for each _Nc chip and deletes the guard interval from each chip block;
An FFT unit that decomposes the chip series of each chip block from the deletion unit into N _c orthogonal frequency components by N _c -point FFT;
N _c pieces of provided for each orthogonal frequency components, and N _c pieces of differential decoder for differentially decoding the respective frequency components from the FFT unit,
N _c pieces of provided for each orthogonal frequency components, the output from the differential decoder, the N _c pieces of equalizer that performs equalization for each frequency component,
An adder for adding N _c frequency components from each of the equalization units;
A CDMA transmission apparatus comprising: a symbol determination unit that obtains a reception data symbol corresponding to a transmission data symbol. A spreading factor SF indicating the number of chips per data symbol is equal to the number of points N _{c of the} FFT unit, or
2. The CDMA transmission apparatus according to claim 1, wherein the number of transmission data symbols included in each chip block is one. In the differential decoding unit and the equalization unit of the kth (k = 0 to N _c −1) frequency component, the orthogonal frequency component R _m (k) of the current chip block and the previous chip block The CDMA transmission apparatus according to claim 1 or 2, wherein differential decoding and equalization are performed as follows using the orthogonal frequency component R _m-1 (k).
_{S ^ m (k) = w} m (k) R m (k) R * m-1 (k) (5)
Here, * is a complex conjugate, and w _m (k) is an equalization weight. 4. The CDMA transmission apparatus according to claim 1, wherein the equalization unit creates the equalization weight w _m (k) using one of the following equations.

Here, ZF represents zero forcing, and MMSE represents the minimum mean square error. C _m (k) is a component of the k-th frequency of the spread code c _m (t). σ ² is noise power.   The CDMA transmission apparatus according to claim 4, further comprising a measuring unit for measuring noise power for each frequency component of the FFT unit. For each m-th chip block, a transmission data symbol sequence {a _{m, n} ; n = 0 to (N _c / N _c ) consisting of N _c / SF symbols (N _c is the number of FFT points and SF is a spreading factor). SF) -1} multiplied by the spreading code c _m (t);
An FFT unit for decomposing the m-th chip block composed of N _c chips obtained by the spreading unit into N _c orthogonal frequency components by N _c -point FFT;
N _c pieces of provided for each frequency component, and N _c pieces of differential encoding portion for obtaining a differential coding the frequency components of each frequency component by differential coding,
The N _c pieces of differential coding the frequency components from the differential encoding unit, N c _- and IFFT unit obtaining a time domain signal of the chip blocks by applying the point IFFT consisting N _c chips,
An additional unit that copies a predetermined amount of chips at the end of the time domain signal of the chip block consisting of _Nc chips from the IFFT unit and adds it to the head of each chip block as a guard interval;
A transmitting unit for transmitting a chip block sequence to which a guard interval from the adding unit is added;
A CDMA transmission apparatus on the transmission side comprising: A receiving unit that samples the received signal for each chip time and obtains a chip sequence of the received frequency domain differentially encoded signal;
A deletion unit that divides the chip series from the reception unit into chip blocks for each N _c chip (N _c is the number of FFT points), and deletes a guard interval from each chip block;
An FFT unit that decomposes the chip series of each chip block from the deletion unit into N _c orthogonal frequency components by N _c -point FFT;
N _c pieces of provided for each orthogonal frequency components, and N _c pieces of differential decoder for differentially decoding the respective frequency components from the FFT unit,
N _c pieces of provided for each orthogonal frequency components, the output from the differential decoder, the N _c pieces of equalization unit that performs frequency domain equalization for each frequency component,
An IFFT unit obtaining a time domain signal of _{N c} chip by applying the point IFFT, - _{N c} to _{N c} number of frequency components from the equalization unit
A despreading unit that despreads the output of the IFFT unit with a spreading code;
An integration unit that integrates the output of the despreading unit for each number of chips per data symbol;
A receiving-side CDMA transmission apparatus comprising: a symbol determination unit that obtains reception data symbols corresponding to transmission data symbols am _{, n} . A transmitting-side CDMA transmission apparatus according to claim 6;
A CDMA transmission apparatus comprising the receiving side CDMA transmission apparatus according to claim 7. The spreading factor SF, which is the number of chips per data symbol, is smaller than the number of FFT points N _c ;
Or
9. The CDMA transmission apparatus according to claim 6, wherein the number of transmission data included in each chip block is two or more. The differential encoding unit of the k-th (k = 0 to N _c −1) frequency component is:
A one _- block delay unit for obtaining the k-th frequency component T _m−1 (k) obtained by differential encoding of the previous chip block;
A normalization unit that normalizes the amplitude of the k-th frequency component from the one-block delay unit;
A divider that divides the orthogonal frequency component S _m (k) of the current chip block by the output from the normalization unit;
The CDMA transmission apparatus according to claim 6, further comprising: In the differential decoding unit and the equalization unit of the kth (k = 0 to N _c −1) frequency component, the orthogonal frequency component R _m (k) of the current chip block and the previous chip block 9. The CDMA transmission apparatus according to claim 6, wherein differential decoding and equalization are performed as follows using the orthogonal frequency component R _m-1 (k).
_{S ^ m (k) = w} m (k) R m (k) R * m-1 (k) (5)
Here, * is a complex conjugate, and w _m (k) is an equalization weight. The CDMA transmission apparatus according to claim 6, further comprising an equalization weight creating unit that creates the equalization weight w _m (k) using any one of the following equations.

Here, ZF represents zero forcing, and MMSE represents the minimum mean square error. σ ² is noise power.
R _m−1 (k) is an orthogonal frequency component of the immediately preceding chip block. S ^to _m−1 (k) are components of the k-th frequency obtained by spreading the received data symbol obtained by receiving the previous chip block and performing FFT. The equalization weight creating unit
A second one-block delay unit for obtaining a received data symbol sequence of a chip block immediately preceding the received data symbol sequence;
A second spreading unit for spreading the data symbols from the previous one-block delay unit;
A second FFT unit that performs N _c -point FFT on the time domain signal from the second spreading unit;
_Nc frequency components are provided for each of the _Nc frequency components, and based on the frequency components S ^to _m-1 (k) of the second FFT unit, using a predetermined ZF or MMSE, using equation (3), etc. N _c equalization weight calculators for obtaining equalization weights w _m (k) from frequency components from the second FFT unit;
The CDMA transmission apparatus according to claim 12, further comprising: On the sending side,
The transmission data sequence is data modulated to obtain a data symbol sequence,
Differential encoding the data symbol sequence to obtain a differential encoded data symbol sequence,
Multiplying the differentially encoded data symbol sequence by a spreading code to obtain a chip block consisting of N _c chips (N _c is the number of FFT points),
Copy the specified chip at the end of each chip block and add it to the beginning of that block as a guard interval,
Send chip block sequence with guard interval added,
On the other hand, on the receiving side,
Receiving the chip block sequence from the transmitting side, sampling the received signal every chip time to obtain a chip sequence,
Dividing the chip series into chip blocks for each _Nc chip, and removing the guard interval from each chip block;
The chip sequence for each chip block which the guard interval has been deleted N _c - decomposed into N _c pieces of orthogonal frequency components by the point FFT,
For each of the N _c orthogonal frequency components, each frequency component is differentially decoded,
For each of the _Nc orthogonal frequency components, the differentially decoded output is equalized for each frequency component;
Add each equalized _Nc frequency components,
A CDMA transmission method for obtaining a received data symbol corresponding to a transmitted data symbol. For each m-th chip block, a transmission data symbol sequence {a _{m, n} ; n = 0 to (N _c / N _c ) consisting of N _c / SF symbols (N _c is the number of FFT points and SF is a spreading factor). SF) −1} is multiplied by the spreading code c _m (t),
The resulting N _c consisting chips m th chip block N _c - decomposed into N _c pieces of orthogonal frequency components by the point FFT,
For each of the _Nc frequency components, each frequency component is differentially encoded to obtain a differentially encoded frequency component,
The N _c pieces of differential coding the frequency components, N c _- to obtain a time domain signal of the chip block of N _c chip by applying the point IFFT,
A portion of the time domain signal at the end of the chip block consisting of _Nc chips is copied and added as a guard interval to the beginning of each chip block,
A transmitting-side CDMA transmission method for transmitting a chip block sequence to which a guard interval is added. The received signal is sampled at every chip time to obtain a chip sequence of the received frequency domain differentially encoded signal,
The chip series is divided into chip blocks every N _c chips (N _c is the number of FFT points), and the guard interval is deleted from each chip block,
The chip sequence for each said chip block N _c - decomposed into N _c pieces of orthogonal frequency components by the point FFT,
For each of the _Nc orthogonal frequency components, differentially decode each frequency component;
Perform frequency domain equalization for each frequency component on the differentially decoded output for each of N _c orthogonal frequency components,
To obtain a time domain signal of N _c chip by applying the point IFFT, - the equalized N _c number of frequency components N _c
The IFFT output is despread with a spreading code,
For the despread output, integrate for each number of chips per data symbol,
A CDMA transmission method on the reception side for obtaining reception data symbols corresponding to transmission data symbols am _{, n} . CDMA transmission method on the transmission side according to claim 15,
A CDMA transmission method including the receiving-side CDMA transmission method according to claim 16.

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