JPH07336323A - Code division multiple access equipment - Google Patents

Abstract

PURPOSE:To reduce the transmission error rate of plural CDMA equipments present in a transmitter. CONSTITUTION:On a transmission side, so as to orthogonalize the spreading codes of a spreading code generation part 11 for transmission data, the orthogonal codes of an orthogonal code generation part 12 are multipled in a code product generation part 13 and the spreading codes are generated. In spreading modulation parts 14-1-14-K, the spreading codes generated in the code product generation part 13 are used and the plural transmission data are spread. The respective transmission data are added in an addition part 15, superimposed on carrier waves in a multipled product modulation part 17 and radio transmitted. On a reception side, the base band signals of carrier wave components are extracted in a low-pass filter part 24. The spreading codes of the spreading code generation part 25 and the orthogonal codes of the orthogonal code generation part 26 are multipled in the code product generation part 27 and the spreading codes are generated. In a correlation arithmetic operation part 28, the correlation arithmetic operation of the base band signals and the spreading codes is performed and a correlation arithmetic value is outputted as demodulation data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for code division multiple access (hereinafter referred to as CDMA) communication, for example, CDMA communication in mobile communication such as personal communication service (hereinafter referred to as PCS) and digital cellular. Therefore, CDMA is designed to reduce the influence of interference when a plurality of transmission data exist in one transmitting station.
It relates to the device.

[0002]

2. Description of the Related Art As a CDMA device in CDMA communication, for example, there is one described in the following documents. Reference: Joint Technical Committee (JTC) 1-5 (199
3-1) Phoenix (US) Donald Grieco, Gary lomp and
Kourosh Parsa “Radio System Characterization (Respon
se to JTC (AIR) /93.05.13-133R1)] ”JTC (AIR) /93.11.0
1.413, P.22-27 In the CDMA device of the above-mentioned document, each transmission station, synchronization data, and control data for one transmitting station, and corresponding pseudo noise (Pseudo noise) corresponding to a plurality of transmission data are present.
Noise, hereinafter referred to as PN) Create a spreading code with a code. Then, a plurality of transmission data of transmission data, synchronization data, and control data in the transmission data are multiplied by these PN spreading codes, respectively, to generate a spread-modulated baseband signal. The baseband signal is generated by dividing the signal obtained by adding the transmission data and the synchronization data into the in-phase signal of the orthogonal carrier wave and the signal obtained by adding the transmission data and the control data, and making the orthogonal signal. Radio frequency (hereinafter,
It is modulated in the RF band. As a result, the transmission data, the synchronization data, and the control data are communicated with a plurality of transmission data.

[0003]

However, the conventional CDMA device has the following problems and it is difficult to solve them. In a conventional CDMA device, when a non-orthogonal code such as a PN code is used as a spreading code of transmission data that exists in one transmitting station, it is not only in the other station but also in the own station as an essential problem. Due to the plurality of transmission data existing, when one transmission data of one transmission station is focused on, all other transmission data of the transmission station cannot be completely removed. Therefore, since the transmission data that is not removed is added to the reception data as an interference wave, the amount of interference increases as the number of transmission data of the transmitting station increases, and there is a problem that an error occurs in the reception data.

[0004]

In order to solve the above problems, the present invention spreads transmission data using a spreading code having a wider frequency band than the transmission data, and wirelessly uses this as a baseband transmission signal. CD to send over the line
In a CDMA device using the MA method, a transmission side is provided with a spreading code generation means, a baseband signal generation means, and a transmission signal generation means, and a reception side is provided with a reception data generation means and a calculation means. Here, the spreading code generating means orthogonalizes an integer multiple of the length of the spreading code unique to the transmitting station, which corresponds to a number corresponding to a plurality of existing transmission data. The code is multiplied by the generated data to generate the spread code corresponding to the plurality of existing transmission data. The baseband signal generating means generates a baseband signal by multiplying the spreading code corresponding to the plurality of existing transmission data by each of the plural transmission data, and the transmission signal generating means further comprises: The transmission signal in the RF band is generated from the baseband signal and a carrier wave. The reception data creating means creates reception data in the base band from the received signal in the RF band. In addition, the calculating means creates data for which a spreading code peculiar to the transmitting station is created and orthogonal codes which are an integral multiple of the length of the spreading code peculiar to the transmitting station, which corresponds to a number corresponding to a plurality of existing transmission data. And the spread data corresponding to the plurality of existing transmission data are generated, and the spreading code and the received data of the baseband band are respectively multiplied to obtain a plurality of existing transmission data. Is output as the estimated value of the received data.

[0005]

It is assumed that a pair of transmission / reception stations having transmission data existing in one transmission station are completely synchronized.
Each input transmission data is directly spread by each spreading code. Consider a case where the spreading code used for one symbol (plus 1 or minus 1 symbol) of input transmission data has a constant length. As a general tendency, when a non-orthogonal spreading code is used, when a plurality of transmission data exist in one transmitting station, the error rate increases as the number of transmission data increases.
When orthogonal spreading codes are used, if multiple transmission data are equal to or less than the number of orthogonal spreading codes in one transmitting station, each transmission data becomes an uncorrelated signal due to orthogonalization, so errors are suppressed. It becomes possible to do. Therefore,
There is a close relationship between the number of users and the spreading code used per symbol of transmitted data and its length. In the present invention, the spreading code generation means generates a spreading code ck [i] (t) for one symbol (where i is the transmission station and k is the transmission data existing in the transmission station) for the spreading code ck [i]. ] (t) is multiplied by an orthogonal code having an integral multiple of length to orthogonalize the spread code of one symbol of the input transmission data.
Using these orthogonalized codes, the baseband signal generation means spreads the input transmission data existing in a certain transmission station to generate a spread signal (baseband signal), and sends it to the transmission signal generation means. . The transmission signal generation means multiplies each of the spread baseband signals by a carrier wave and the like to create and transmit a transmission signal in the RF band. The reception data creation means on the reception side creates reception data in the baseband from the received signal in the RF band, and sends it to the calculation means. The calculating means multiplies the created spreading code by an orthogonal code that is an integral multiple of the length of the spreading code to generate a spreading code, multiplies the spreading code by the received data in the baseband, and It is output as the received data estimation value of the existing transmission data.

As described above, in the present invention, one spreading code unique to the transmitting station and the orthogonal code which is an integral multiple of the spreading code are used as the spreading codes of the transmission data existing in plural in one transmitting station. By this, cross-correlation of a plurality of transmission data existing in one transmission station is suppressed (that is, even if the transmission data in one transmission station increases, the cross-correlation of the transmission data is suppressed). The interference signal from other transmission data is reduced, and the error rate of the reception data is reduced. Therefore, the above problem can be solved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of a CDMA device in an embodiment of the present invention will be described. The transmission signal S [i] (i) in the RF band, although the transmission data existing in plural in one certain transmitting station are completely synchronized, is expressed by the following equation (1).

[0008]

[Equation 1] In the equation (1), ak [i] (t) is the transmission data (information data) transmitted by the transmission data k (k = 1 to K) of the i station at the time t, and is plus 1 or minus 1. expressed. This transmission data ak [i] (t) does not change during the symbol long time Ta. ck [i] (t) is a spreading code at time t and is N (Ta = N) for one symbol length.
・ Tc, where Tc has a speed twice as long as the spreading code chip time. wk [i] (t) is an orthogonal code at time t, and is an integral multiple L · N (Ta = L ·
N · Tw, where Tw is the speed of the orthogonal code chip time) times. Further, ψ [i] (t) is a carrier wave at time t. The received signal R (t) in the RF band transmitted in the carrier band in the spread spectrum communication is expressed by the following equation (2) when the number of transmitting stations is M.

[0009]

[Equation 2] When detecting the signal of station i in the 1-symbol section,
By performing the multiplication processing, the component in the baseband which is put on the carrier ψ [i] (t) from the received signal R (t) in the RF band.
Extract E (t). Note that E (t) is the transmission spread modulation data ak [i] (t) · ck [i] (t) · of all transmitting stations in the equation (1).
Corresponds to wk [i] (t). Then, the spreading code ck [i] (t) · wk [i] used in the transmitting station i and synchronized with the transmitting station i.
The correlation value with (t) is calculated, and the sum bk [i] thereof is calculated (this is called despreading processing). The sum bk [i] obtained by such a correlation calculation, that is, the output of the transmission data component on the carrier ψ [i] (t) is expressed by the following equation (3).

[0010]

[Equation 3] Therefore, the sum bk [i] of the correlation values is the orthogonal code wk of the equation (3).
When an orthogonal code such as the Walsh-Hadamard code is used for [i] (t), the cross-correlation value of each code can be suppressed. This indicates that it is possible to separate the transmission data (that is, the sum of correlation values) bk [i] received from the same transmitting station i, and at the same time, it becomes the reception data estimation value. 1 and 2 show an example of the configuration of the CDMA device of this embodiment constructed based on the above principle. FIG. 1 is a functional block diagram on the transmitting side of a CDMA apparatus showing an embodiment of the present invention, and FIG. 2 is a functional block diagram on the receiving side. This CDMA device is composed of a digital signal processor (hereinafter referred to as DSP), an individual circuit using an integrated circuit, and the like. On the transmission side of the CDMA device shown in FIG. 1, a spreading code generator 11 that generates a spreading code ck [i] (t) (where k = 1 to K) and an orthogonal code wk [i] (t) are generated. The orthogonal code generator 12 is provided, which is connected to the input side of the code product generator 13. The code product generation unit 13 multiplies the spread code ck [i] (t) and the orthogonal code wk [i] (t) to generate the spread code ck [i] (t) · wk [i] (t). And the output side thereof has a plurality of spread modulators 14-1.
It is connected to the input side of 14-K.

The plurality of spread modulators 14-1 to 14-K are
The input transmission data ak [i] (t) (where k = 1 to K) and the spreading code ck [i] (t) .wk [i] (t) are spread by multiplication to obtain the baseband signal, It has a function of generating the spreading code dk [i] (t). Multiple spread modulators 14-1 to 14-K
Are composed of the same elements for modulation by dividing into the number of sequences according to the number of input transmission data, and the addition section 15 is connected to the output side thereof. The input side of the product modulation section 17 is connected to the output side of the addition section 15 and the output side of the carrier wave generation section 16 that generates the carrier wave ψ [i] (t). The product modulation unit 17 has a function of multiplying the spread code dk [i] (t) and the carrier ψ [i] (t) and outputting the RF band transmission signal sk [i] (t). The transmitting antenna 18 is connected to its output side. Here, the spreading code generation unit 11, the orthogonal code generation unit 12, and the code product generation unit 13 constitute a spreading code generation unit, and the spreading modulation units 14-1 to 14-K and the addition unit 15 form a baseband signal generation unit. Is configured. Further, the carrier wave generator 16 and the product modulator 17 constitute a transmission signal generating means. The receiving side of the CDMA device shown in FIG. 2 is provided with a receiving antenna 21 for receiving a received signal R (t) in the RF band and a carrier wave generation unit 22 for generating a carrier wave ψ [i] (t), which are multiplied by each other. Product demodulator 23
Is connected to the input side of. The product demodulation unit 23 has a function of multiplying the received signal R (t) by the carrier wave ψ [i] (t) and outputting a product signal U (t). The input side of the low-pass filter unit 24 that removes the high-frequency component of the signal U (t) and outputs the baseband signal E (t) is connected. The spreading code ck [i] is sent to the receiving side of this CDMA device.
Spreading code generator 25 for generating (t) and orthogonal code wk
and an orthogonal code generator 26 that generates [i] (t),
Their output side is connected to the input side of the chord product generator 27. The code product generation unit 27 uses the spread code ck [i] (t)
And the orthogonal code wk [i] (t) are spread by multiplication to generate a spread code ck [i] (t) · wk [i] (t), the output side of which is the correlation calculation unit 28. It is connected to the input side. The correlation calculator 28 calculates the baseband signal E (t) and the spreading code ck.
[i] (t) ・ wk [i] (t) Correlation calculation is performed and sum of correlation values bk [i]
Is output as a received data estimation value (that is, demodulation estimation data). Here, the carrier wave generator 22,
The product demodulation unit 23 and the low-pass filter unit 24 constitute reception data creating means. Further, the spreading code generating section 25, the orthogonal code generating section 26, the code product generating section 27, and the correlation calculating section 28 constitute a calculating means. The operation (1) on the receiving side and the operation (2) on the transmitting side of the CDMA apparatus configured as above will be described below.

(1) Operation on the transmitting side in FIG. 1 Here, it is assumed that a plurality of transmission data in the transmitting station are completely synchronized. When performing transmission, the input transmission data ak [i] (t) is input to each of the spread modulation units 14-1 to 14-K. On the other hand, in the spreading code generator 11,
A spreading code ck [i] (t) for using a plurality of transmission data of the transmitting station in spreading modulation is generated and sent to the code product generating unit 13. This spreading code ck [i] (t) is an orthogonal code such as the Walsh Hadamard code, P
The spreading code is a non-orthogonal code such as a block code sequence such as N code, Gold code, or BCH code. Further, in the orthogonal code generator 12, an orthogonal code wk [i] (t) used to orthogonalize each input transmission data after spread modulation using the orthogonal code with the plurality of input transmission data k in the transmitting station i. Is generated and sent to the chord product generator 13. This orthogonal code wk [i]
For (t), an orthogonal code such as Walsh Hadamard code can be used. The code product generator 13 multiplies the spread code ck [i] (t) by the orthogonal code wk [i] (t), and spread code ck [i] (t) · wk of each input transmission data k.
[i] (t) is generated and the spreading code ck [i] (t) · wk [i] (t) is input to each of the plurality of spreading modulation units 14-1 to 14-K. The plurality of spread modulators 14-1 to 14-K spread the input transmission data ak [i] (t) and the spread code ck [i] (t) · wk [i] (t) by multiplication, and then A spread code dk [i] (t) which is a baseband signal as shown in Expression (4) is generated. dk [i] (t) ＝ ak [i] (t) ・ ck [i] (t) ・ wk [i] (t) (4) Multiple spread codes dk [i] (t) , And is added by the adder 15 and sent to the product modulator 17. In the product modulator 17,
The spread code dk [i] (t) output from the adder 15 is multiplied by the carrier ψ [i] (t) output from the carrier generator 16 to obtain the RF band represented by the following equation (5). The transmission signal sk [i] (t) is generated and output through the transmission antenna 18. sk [i] (t) = dk [i] (t) · ψ [i] (t) (5) (2) Operation on the receiving side in FIG. 2 Here, each transmission of each transmitting station The receiving stations for the data are assumed to be perfectly synchronized. In the operation on the receiving side, R expressed by the equation (2) sent from the transmitting side is used.
The reception signal R (t) of the F band is received by the reception antenna 21,
It is sent to the product demodulation unit 23. The product demodulation unit 23 multiplies the reception signal R (t) received by the reception antenna 21 and the carrier wave ψ [i] (t) output from the carrier wave generation unit 23, and the result is expressed by the following equation (6). The multiplied product signal U (t) is output and sent to the low-pass filter unit 24. U (t) = R (t) ψ [i] (t) (6) In the low-pass filter unit 24, ψ of the carrier ψ [i] (t) included in the product signal U (t) is calculated. The baseband signal E (t) added to the [i] component is extracted and sent to the correlation calculation unit 28. On the other hand, the spreading code generator 25 uses the spreading code ck that is used by the transmitting station i station and is synchronized with the respective transmission data of the transmitting station i station.
[i] (t) is generated and given to the chord product generator 27. Further, in the orthogonal code generation unit 26, the orthogonal code wk [i] (t) used to orthogonalize the plurality of input transmission data k in the transmitting station i by using the orthogonal code.
Is generated and given to the chord product generator 27. The code product generation unit 27 spreads the spread code ck [i] (t) input and the orthogonal code wk [i] (t) by multiplication to spread the spread code ck [i] (t) of each input data k. ) · Wk [i] (t) is generated and sent to the correlation calculation unit 28. In the correlation calculation unit 28, the baseband signal E (t) output from the low pass filter unit 24,
Input transmission data ak output from the chord product generator 27
Correlation calculation with spread code ck [i] (t) ・ wk [i] (t) corresponding to [i] (t) is performed, and sum bk [i] of correlation values as shown in equation (3) is demodulated. Output as estimated data. This demodulation estimation data is
When an orthogonal code such as a Walsh Hadamard code is used as the orthogonal code wk [i] (t) in the equation (3), the cross-correlation value of each code can be suppressed. This indicates that the transmission data bk [i] transmitted from the same transmitting station i can be separated.

As described above, in this embodiment, the spreading code ck [i] (t) used for each input transmission data ak [i] (t) of the transmitting station.
Is orthogonalized by using the orthogonal code wk [i] (t), even if the number of transmission data of the transmitting station increases (that is, even if the number of simultaneous transmission data of the same transmitting station increases), Spread code ck [i] (t) ・ wk [i] in each transmission data communication of the station
The cross-correlation value of (t) can be suppressed. Therefore, it is possible to reduce the error rate of the received data on the receiving side. The present invention is not limited to the above embodiment, and various modifications can be made. The following are examples of such modifications. (A) In FIG. 1, a spreading code generating unit including a spreading code generating unit 11, an orthogonal code generating unit 12, and a code product generating unit 13, a spreading modulation unit 14-1 to 14-K, and an adding unit 15 are used. The baseband signal generation means and the transmission signal generation means composed of the carrier wave generation section 16 and the product modulation section 17 may be modified into configurations other than those shown in the drawings. (B) In FIG. 2, received data creating means composed of a carrier generating section 22, a product demodulating section 23, and a low-pass filter section 24, a spreading code generating section 25, an orthogonal code generating section 26, and a code product generating section 27. The calculation means configured by the correlation calculation unit 28 may be modified into a configuration other than that illustrated. (C) In FIG. 1 and FIG. 2, the transmitting antenna 18 and the receiving antenna 21 are provided. However, circuits of the receiving side and the transmitting side thereof are provided in the terminal, and the transmitting antenna 18 and the receiving antenna 21 are provided as one. The antenna may be shared, and a duplexer may be provided in the antenna to switch between transmission and reception.

[0014]

As described in detail above, according to the present invention, the transmitting side is provided with the spreading code generating means, the baseband signal generating means, and the transmitting signal generating means, and the receiving side is provided with
Since the reception data creation means and the calculation means are provided, even if the number of transmission data of the transmitting station is increased by orthogonalizing the spreading code used for each transmission data of the transmitting station using the orthogonal code (that is, , Even if the number of simultaneous transmission data in the same transmitting station increases, the cross-correlation value of the spreading code in each transmitting data communication of the transmitting station can be suppressed. Therefore, the error rate of received data can be reduced.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a transmission side of a CDMA device showing an embodiment of the present invention.

FIG. 2 is a functional block diagram of a receiving side of a CDMA device showing an embodiment of the present invention.

[Explanation of symbols]

 11, 25 Spreading code generating section 12, 26 Orthogonal code generating section 13, 27 Code product generating section 14-1 to 14-K Spreading modulation section 15 Addition section 16, 22 Carrier generation section 17 Multiplying modulation section 18 Transmission antenna 21 Reception Antenna 23 Multiplier demodulator 24 Low-pass filter 28 Correlation calculator

Front page continued (72) Inventor Takuro Sato 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. Code division using a code division multiple access method, in which transmission data is spread using a spreading code having a wider frequency band than the transmission data and is transmitted as a baseband transmission signal via a radio circuit. In the multiple access device, on the transmitting side, the data for which the spreading code unique to the transmitting station is created and the integer multiple of the length of the spreading code unique to the transmitting station, which corresponds to the number corresponding to the plural existing transmission data, are transmitted. Spreading code generation means for multiplying the orthogonal code created data and generating the spreading code corresponding to the plurality of existing transmission data; and a plurality of spreading codes corresponding to the plurality of existing transmission data Baseband signal generation means for generating a baseband signal by multiplying each of the existing transmission data, and a baseband signal generating means for generating a baseband signal. A transmission signal generation means for generating and transmitting the transmission signal in the frequency band, and the reception side, on the reception side, reception data generation means for generating reception data in the baseband from the received signal in the radio frequency band, and transmission Multiply the data for which a spread code unique to a station is created by the data for which an orthogonal code that is an integer multiple of the length of the spread code unique to the sending station, which corresponds to the number corresponding to a plurality of existing transmission data, is created. , Generating a spreading code corresponding to the plurality of existing transmission data, multiplying the spreading code by the received data of the base band, and outputting as a received data estimation value of the plurality of existing transmission data. A code division multiple access device, comprising: