JP2003348051A - Spread spectrum communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control reception according to transmission rate, etc., to be demanded for transmission data and to mitigate effects caused by characteristics degradation due to complication of mutual correlation and multipath phasing. <P>SOLUTION: The transmission data distributed to a plurality of channels are distributed to the first to the (k+1)th data streams regarding the channels, a spreading code of k is selected according to the (k+1)th data stream among m candidates allocated from candidates for the spreading code with code length of n, a spread spectrum signals of a plurality of the channels is formed by a fact that a signal in which the information is modulated by the first to the k-the data streams is spread by using the selected spreading code of k, the spread spectrum signals of a plurality of the channels with different carriers or a transmission signal of a sub-carrier are received and information for controlling m candidates for the spreading code with the code length of n and a value of k as common ones to the respective channels is received. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transmission of multimedia data having large fluctuations such as low-speed, large-capacity data, real-time and large-capacity data such as audio data, computer-processed data, and moving image data by different transmission methods. The present invention relates to a spread-spectrum communication method that can be efficiently handled at a rate.

[0002]

2. Description of the Related Art In order to perform multimedia communication, data that can be communicated at a low transmission rate of about several tens of kbps (bits / second) such as audio data and high transmission of several Mbps or more such as moving image data are used. It is required that the same communication system handles data up to the rate data.

In recent years, a code division multiple access (CDMA) system has attracted attention as a system capable of user multiplexing using the same band. This CDMA system is a spread spectrum (SS) communication system, and realizes user multiplexing within the same band by multiplying each symbol with a different spreading code for each user. The adoption of this CDMA system has also been decided in the standardization of IMT2000 by the International Telecommunication Union (ITU).

Conventionally, the following three methods have been considered for transmitting at various transmission rates using the CDMA system. The first method is a “spread code multiplexing method” in which a certain user uses a plurality of spread codes. Thereby, even if the transmission rate for each spread code is fixed, various transmission rates can be realized by changing the number of multiplexed spread codes.
The second method is a method of changing the number of data within a predetermined time (frame) using one spreading code. Second
As a main means for realizing the above method, there is a "variable spreading factor transmission system" in which the spreading code length (spreading code cycle) is changed while the code rate (chip rate) is kept constant. As a third method,
By combining the first and second methods described above,
It is possible to realize from low-speed transmission to high-speed transmission, and IMT2000 (International Mobile Telecomunications
-2000) realizes a variable transmission rate with these combinations. Hereinafter, a communication system combining the “spreading code multiplexing method” and the “variable spreading factor transmission method” will be described.

FIG. 12 is a block diagram of a conventional spread spectrum communication system. In the figure, 41 is user 1
Of the transmitter. The transmitters of the plurality of users 1 to u have the same configuration. In IMT2000, spreading is performed using a long code for the purpose of cell identification and the like. Further, although transmission power control is performed, the description thereof is omitted. In the transmitter 41, reference numeral 42 denotes a serial / parallel converter for distributing input data to one or more systems of data. The data sequence of each system passes through an encoding unit 1, an interleave unit 2, an information modulation unit 4, and a spreading unit 43, is added by an addition unit 44, becomes a transmission signal through a radio circuit unit 45, and is transmitted from an antenna (not shown). Is done.

[0006] The number of systems in the serial / parallel converter 42 and the spreading code length n in the spreading section 43 are controlled by rate information data specifying the transmission rate of input data. The rate information data is sent to the receiver 46, and a process opposite to that on the transmitting side is performed using the rate information data.

[0007] On the other hand, 46 is a receiver of the user u as a communication partner of the user 1. The receivers of a plurality of users 1 to u have the same configuration. In the receiver 46, reference numeral 47 denotes a radio circuit unit, which branches and outputs the quadrature demodulated baseband signals of the I component and the Q component to the despreading units 48 of a plurality of systems. The outputs of the despreading units 48 of the respective systems are processed by the information demodulation unit 11, the deinterleaving unit 14, and the decoding unit 15, respectively, and reconstructed by the parallel / serial conversion unit 49, corresponding to the input data on the transmission side. Output data is obtained. The number of systems in the serial / parallel converter 42 and the spreading code length n in the despreading unit 48 are controlled by receiving the rate information data transmitted from the transmitter 41.

FIG. 13 is an explanatory diagram of a spread code used in the conventional spread spectrum communication system shown in FIG. FIGS. 13A to 13D show spreading code candidates with spreading code lengths n = 16, 8, 4, and 2, respectively. In each code length, a plurality of spreading codes are used according to the number of multiplexed spreading codes.

FIG. 14 is an explanatory diagram of the code generation principle of the spread code shown in FIG. Spreading codes with different code lengths are
It has a wooden structure. The first spreading code having a code length of 2 is “11” obtained by adding the same code “1” to the upper-layer code “1”, and the second spreading code is the upper-layer code “1”. ”With its complement“ 0 ”added to“ 10 ”. The first spreading code having a code length of 4 is “1111” obtained by adding the same code “11” to the first code “11” of the upper hierarchy, and the second spreading code is the upper hierarchy. It is “1100” obtained by adding the complement “00” to the first code “11”. The third one is “10” in which the same code “10” is added to the second code “10” in the upper layer.
10 ", and the fourth one is the second one in the higher hierarchy.
"100" obtained by adding the complement "01" to the code "10"
1 ". Similarly, a spread code having a code length of 16 provides 16 spread code candidates, but a description thereof will be omitted.

[0010] The spreading code generated by the above method is called a hierarchical orthogonal code. Spreading codes in the same hierarchy are orthogonal. For spreading codes that are not in the same hierarchy, those that are not in the same branch maintain orthogonality. In other words,
When the spreading code at the top of the tree structure is used, the spreading codes on the branches below it cannot be used at the same time.

Returning to FIG. 12, the description will be continued. For input data such as audio and moving images, a “code multiplexing method” according to the rate information data is used. That is, the serial / parallel conversion unit 42 encodes the encoding unit 1 according to the transmission code multiplexing number.
Are distributed to a plurality of circuits. Here, when the number of multiplexed transmission codes is 1, code multiplexing is not performed, so that the data is output to only one encoding unit 1. The distributed data of each system undergoes processing such as convolutional encoding in each encoding unit 1. The data of each system after encoding is interleaved in a predetermined frame unit in the interleave unit 2 in order to reduce the influence of fading fluctuation, and then the information modulation unit 4 performs QPSK (Quadrature Phase Shift Key).
ing) Information modulation such as modulation is performed, and the subsequent spreading section 43 uses spreading codes with different spreading code lengths n,
Performs spread spectrum processing.

The spread output of each system of the user 1 is added to an adder 4
The signal is added at 4 and becomes a transmission signal at the wireless circuit section 45. All users from user 1 to user u perform similar processing using a different spreading code for each user, thereby realizing user multiplexing. In order to realize the “variable spreading factor transmission method”, the spreading unit 43 changes the spreading code length n while keeping the chip rate constant. Since the symbol rate changes accordingly, the processing time for one symbol of information modulation is changed. Therefore, other processing blocks also need to be changed. The processing for the “variable spreading factor transmission method” and the processing change for changing the “number of code multiplexes” are performed by the rate information data.

On the other hand, in the receiver 46, the received signal is converted into a baseband signal by the radio circuit section 47. Thereafter, a plurality of despreading units 48 are provided in accordance with the number of multiplexed spreading codes.
Then, despreading is performed using the spreading code of code length n used in the spreading unit 43. Subsequently, the information demodulation unit 11 performs level judgment on the I and Q components of each system and demodulates them.
The demodulated data of each system is restored by the deinterleave unit 14 to obtain data in which the influence of fading fluctuation is reduced. For the data of each system, the decoding unit 15 decodes the convolutional code, and the parallel / serial conversion unit 49 returns the data to serial data to reconstruct the output data. Similarly to the transmitter 41, the despreading unit 48, the information demodulation unit 11, the deinterleaving unit 14, and the decoding unit 15 are processing circuits according to the change of the spreading code length n.

Further, since the transmitter 41 changes the number of code multiplexes and the code length n, it is necessary for the receiver 46 to use some means to make the number of code multiplexes and the code length n known before processing. is there. Therefore, by transmitting the rate information data from the transmitter 41 to the receiver 46 by using any means, the receiver 41 also transmits the rate information data.
Similarly to the above, each process is changed according to the rate information data.

As a specific example of transmitting the rate information data from the transmitter 41 to the receiver 46, first, as a channel different from the user data, the spreading code of this channel is fixed, and the rate information data is transmitted. There is a method of sending. If this other channel is a control channel, it can be transmitted together with data for estimating the propagation state and the like in addition to the rate information data. Second, there is a method in which rate information data is time-multiplexed with user data and transmitted before a rate change is performed. In either case, it is not impossible to change the transmission rate for each symbol, but normally, it is possible to switch by transmitting rate information data in frame units of a predetermined time length.

The interleaving cycle is set to a predetermined time length in consideration of the fading cycle. When the transmission rate changes, the number of symbols per predetermined time and, consequently, the number of bits per predetermined time change. Therefore, the setting of the interleave unit 2 is changed according to the rate information data.

As described above, the setting of the blocks other than the spreading section 43 may be changed by the rate information data depending on the specific processing method. This setting change is similarly applied to other blocks other than the despreading unit 48 of the receiver 46. The base station identification and the user identification are performed based on the type of the long code whose description is omitted or the time difference from the reference timing of the long code.

When the conventional communication system described above is viewed from the aspect of the "spreading code multiplexing transmission system", the influence of cross-correlation increases as the number of spreading codes transmitted simultaneously increases. Particularly, in the uplink of land mobile communication, it is difficult to maintain synchronization between different users, so that there is a problem that characteristic deterioration due to the influence of the cross-correlation becomes remarkable.

FIG. 15 is an explanatory diagram of an example of the auto-correlation and the cross-correlation of the spreading code shown in FIG. The horizontal axis is the phase difference expressed by the number of chips, and the vertical axis is the correlation value. Spreading code 1
, The spreading code 0 is converted to −1 to calculate the correlation value. FIG. 15A shows the spread code “1001011”.
The autocorrelation value of "0", and FIG.
FIG. 9 is a diagram showing a cross-correlation value between “0000” and a spreading code “10010110”.

Since the autocorrelation value shown in FIG. 15A has a code length of 8, peak outputs are obtained at 0, 8, and 16 on the horizontal axis. Such characteristics are shown because orthogonal codes are used as spreading codes. However, even in other places, there are places where the autocorrelation shows a value of 0.5.

The output of the cross-correlation value shown in FIG. 15B is 0 at the same 0, 8, and 16 on the horizontal axis, so that even if the number of code multiplexes of the own station increases, the spread codes are orthogonal. There is no problem. However, when the synchronization between spread codes is shifted from each other, as in the case of spread codes of different users, the cross-correlation value does not become 0 and the intersymbol interference component increases as the number of spread codes used simultaneously increases. Become. Further, as described later, even when the orthogonal code is used as the spreading code, since the main wave and the delayed waves 1 to 3 are not orthogonal, the cross-correlation at the timing of the delayed wave causes
Intersymbol interference increases.

On the other hand, in the downlink, transmission data to other users can be transmitted synchronously, but similar characteristics are deteriorated due to the influence of cross-correlation caused by multipath and interference from other cells.

FIG. 16 is an explanatory diagram of the relationship between a multipath in a multipath propagation path and the conventional spreading code shown in FIG. An example of the delay profile is shown, with the vertical axis representing relative received power and the horizontal axis representing time. Here, the main wave and the delayed wave 1
Here is an example in the case where there is an arrival of 3 from.

(A) to (c) show the spread code, and the spread code cycle is shown in accordance with the time on the horizontal axis. The spreading code of (a) is a spreading code having a spreading code length of 8. Since one symbol is transmitted per spreading code period,
In the case of using QPSK, this spreading code cycle (8 chips) requires 2
Bit data can be transmitted. The transmission rate per chip is 0.25 bits. The spreading code of (b) is a spreading code of code length 2. When the same QPSK is used as information modulation, 2-bit data can be transmitted in each spreading code cycle (2 chips), so that the transmission rate per chip is 1 bit. The spreading code (c) shows a case where four spreading codes having a code length of 8 are multiplexed. When the same QPSK is used as information modulation, 2-bit data can be transmitted with each spreading code, so that the transmission rate per chip is 8 bits.

In the case of the spreading code shown in FIG.
Since the delayed wave 3 is within the spreading period, the main wave and the delayed waves 1 to 3 can be separated in the despreading unit. However, the signals spread by different spreading codes included in the delayed waves 1 to 3 are not synchronized with the spread spectrum signal of the main wave, and thus cause intersymbol interference between the main wave and the delayed waves 1 to 3. . As shown in (c), when four spreading codes are used at the same time, the main wave and the delayed waves 1 to 3 can be separated, but the inter-code interference increases as the number of simultaneous uses increases.

In order to eliminate the influence of such intersymbol interference, an interference elimination technique has conventionally been used. However, in order to eliminate the interference of other users, it is necessary to detect the correlation of other users at the synchronization timing of the own station, and the increase in the number of code multiplexes requires a complicated circuit and an increase in scale. There's a problem.

On the other hand, from the aspect of the “variable spreading factor transmission system”, if code multiplexing is not performed, each user 1 to u
Since transmission is performed using one spread code, there is no complicated cross-correlation unlike the “spread code multiplex transmission method”. Therefore, there is no increase in the complexity or scale of the interference canceling circuit. However, the chip rate is limited by the transmission band, and the spread code length, in other words, the spread code cycle cannot be shorter than the multipath delay time. That is, in FIG.
In the spread code having a code length of 2 shown in (b), since the delayed waves 1 to 3 arrive over the spread code period (2 chips), the main wave and the delayed waves 1 to 3 cannot be simply separated. Therefore, the above-described interference removal circuit becomes complicated. Further, since the symbol transmission rate is determined by the product of the chip rate and the spreading code length, it is not possible to realize a symbol transmission rate higher than this.

By combining the "spreading code multiplexing transmission method" and the "variable spreading factor transmission method" described above, it is also possible to realize high-speed transmission to low-speed transmission. Variable rate is realized by combination. However, when the transmission rate is varied by a combination of these, the intersymbol interference during high-speed transmission remains complicated, and a higher transmission rate, such as about 10 Mb / s, is required as in the case of moving image transmission. In the next generation spread spectrum communication system, there is a problem that the interference canceling circuit needs to be complicated and its scale increased. In order to suppress the circuit scale in the same way as IMT2000, it is conceivable to keep the number of spread code multiplexing low by increasing the chip rate, but the spreading code cycle becomes short,
In an environment of land mobile communication, there is a problem that the interference removal circuit becomes complicated because the multipath exceeds the spreading code period.

[0029]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and can be controlled in accordance with a transmission rate required for transmission data and the like at the time of a high transmission rate. It is an object of the present invention to provide a spread spectrum communication method capable of reducing the effects of multipath fading and deterioration of characteristics due to complicated cross correlation.

[0030]

In order to solve the above-mentioned problems, the present invention provides a spread spectrum communication method having the following configuration. A spread spectrum communication method for transmitting a spread spectrum signal as a plurality of channels and transmitting the spread spectrum signals of the plurality of channels as signals of different carriers or different subcarriers, wherein a plurality of channels for receiving the spread spectrum signal are provided. A spread spectrum communication method for receiving the spread spectrum signals of the plurality of channels as signals of different carriers or different subcarriers, wherein transmission data distributed to the plurality of channels on the transmission side is related to the channels, The (k + 1) -th (k is an integer of 1 or more) data sequence, and m (m is an integer of 2 or more) m allocated from spreading code candidates of code length n (n is an integer of 2 or more) From among the spreading code candidates, the (k + 1) th data k Depending on the data row
Spread signals are selected, and the information-modulated signals are spread by the first to k-th data sequences using the selected k spread codes, respectively.
As the plurality of channels of the spread spectrum signal, the plurality of channels of the spread spectrum signals are received as signals of different carriers or different subcarriers, respectively, while receiving a signal, and inserted into one of the channels, the code length n m spreading code candidates and k
Receiving control information for controlling the value of 共通 as a common value for each of said channels, and for each of said channels,
Despreading using the spreading code candidates and outputting the (k + 1) th data sequence by specifying the k spreading codes selected at the time of transmission based on the despreading output Outputting the first to k-th data strings by demodulating the information of the despread output using the specified k spreading codes; and outputting the first to k-th data strings. reconstructing the k-th data sequence and the (k + 1) -th data sequence for the plurality of channels into reception data, and setting at least one of the n, m, and k values common to each of the channels. Variably controlling according to the control information as a value.

[0031]

FIG. 1 is a block diagram of a first embodiment of the present invention. FIG. 1A shows a transmitter, and FIG.
(B) is a receiver. The transmission / reception operation will be described as a transmitter and a receiver of a plurality of users having the same configuration but different users. In FIG. 1A, reference numeral 1 denotes an encoding unit,
2 is an interleaver, 3 is a distributor, 4 is an information modulator, 5
Denotes a spreading code selection unit, 6 denotes a spreading unit, and 7 denotes a wireless circuit unit. The coding unit 1, the interleaving unit 2, and the information modulating unit 4 are the same as each of the coding unit 1, the interleaving unit 2, and the information modulating unit 4 in FIG. The wireless circuit unit 7 is similar to the wireless circuit unit 45 in FIG. Input data obtained by converting audio, moving images, and the like into digital data is encoded by the encoding unit 1 and the order is changed by the interleaving unit 2. After that, the distributing section 3 converts the interleaved transmission data to 2
Distribute to the system. The data stream of the first system is output to the information modulator 4 in the same manner as in the related art, and a predetermined information modulation, for example, QP
By the SK modulation, two-system modulation data of I and Q is obtained. The data string of the second system is output to the spreading code selection unit 5.

The spreading section 6 spreads the information-modulated data stream of the first system by using a spreading code selected according to the data system of the second system, unlike the prior art. The radio circuit unit 7 becomes an analog transmission signal in which the spread spectrum signal is modulated by a carrier. Also in this embodiment, the spreading code length n used is variable as in the prior art, but in addition, the spreading code generated by the spreading code selection unit 5 and used by the spreading unit 6 is M spreading code candidates are assigned from a plurality of spreading code candidates having a code length of n, and one is selected according to the data sequence of the second system. The number m of the spreading code candidates is variable.
The above values n and m are changed in the spreading code selection unit 5 based on the rate information data. Accordingly, in general, the settings of the encoding unit 1, the interleave unit 2, the distribution unit 3, the information modulation unit 4, and the spreading unit 6 are also controlled based on the rate information data. Note that the technology for transmitting data by selecting one spreading code from a plurality of spreading code candidates is conventionally known as an “M-ary spread spectrum communication system”. It does not control the change of the number m of spreading code candidates to be allocated for the purpose of control.

On the other hand, on the receiver side shown in FIG. 1 (b), 8 is a radio circuit section, 9 _{1 to} 9 _m are despreading sections, 10 is a comparing section, 11
Is an information demodulator, 12 is an information generator, 13 is a reconstructor, 1
4 is a deinterleave unit, and 15 is a decoding unit. The wireless circuit unit 8 is similar to the wireless circuit unit 47 in FIG. The information demodulation unit 11, the deinterleave unit 14, and the decoding unit 15 correspond to the information demodulation unit 11, the deinterleave unit 1 in FIG.
4, the same as that of each one system of the decoding unit 15. m despread unit 9 ₁ to 9 _m, the baseband signal obtained received signal is converted by the wireless circuit section 8 I, and Q components, selected on the transmitting side spreading code candidate (m pieces) Is despread using a spreading code that matches. Here, since the number of spreading code candidates used at the time of selecting a spreading code in the transmitter is set to m, m despreading means are required. Since the value of m is also variable and there are n spreading codes having a spreading code length n, when all the spreading code candidates are used, m =
becomes n, n despread unit 9 ₁ to 9 _n are used.

The comparing unit 10 determines, from among the despread outputs of the plurality of despreading units 9 _{1 to} 9 _m , the spreading code used in one despreading unit that has output the maximum peak value, is most likely. The selected spreading code is determined to be the one that matches the despreading code selected by the transmitter (maximum likelihood determination). The comparing section 10 outputs an output signal (selected despread output signal) despread with the selected spreading code and selection data indicating which despread code is determined. The information generation unit 12 generates second system data used when the spread code selection unit 5 on the transmitter side selects a spread code, according to the selected data. If the comparison unit 10 has the same function as the information generation unit 12, the selection signal output from the comparison unit 10 is immediately output.
It can be the data of the second system.

On the other hand, the selected despread output signal is transmitted to the information demodulation unit 1
1 and outputs a data stream of the first system on the transmission side. The reconstructing unit 13 performs deinterleaving and decoding processes after reconstructing the first and second data strings, thereby obtaining output data. In the above description, QPSK has been described as an example of information modulation, but the information modulation method is not particularly limited. As in the case of BPSK, only the I phase may be used. In the spread modulation, the I-phase and the Q-phase are independently spread-modulated, but the I-phase and the Q-phase may be spread using the same spreading code. Spreading code length n and use the number m of the spreading code candidates to be used, time-change based on the rate information data, despreader 9 ₁ to 9 _m, comparator unit 10 is controlled by the rate information data . Accordingly, the settings of the information demodulation unit 11, the information generation unit 12, the reconfiguration unit 13, the deinterleave unit 14, and the decoding unit 15 may be controlled based on the rate information data.

In the above description, the rate information data is transmitted to the receiver by transmitting it on another channel such as a control channel or by time multiplexing with the information of the user, as in the prior art. This rate information data may be transmitted, for example, in a frame unit having a predetermined time length. The combination of the transmission rate, the spreading code length n of the spreading code candidate to be used, and the number of assignments m is not necessarily 1
No one-to-one correspondence. However, if a correspondence table between the transmission rate and the m spreading code candidates is prepared in the transmitter and the receiver in advance, each numerical value can be determined simply by transmitting the rate information data. As described later, there are cases where spreading code candidates are assigned to a plurality of users. In such a case, the rate information data and the number of users are transmitted, and the above-described correspondence table is also
Create with the number of users as a condition. It is not necessary to transmit the rate information data or the number of users, and any control information that can identify the m spreading code candidates may be used, and the allocated m spreading code candidates themselves may be transmitted to the receiver. .

In the above description, a case has been described in which the transmitter determines each numerical value according to the transmission rate and transmits the rate information data to the receiver. Instead, the transmission rate is transmitted from the reception side to the transmission side, or control information indicating the m spreading code candidates as described above is transmitted to the transmission side, and the transmission side transmits each value according to the received rate information data and the like. A decision may be made.

Next, the characteristic operation of the block configuration shown in FIG. 1 will be specifically described with reference to FIGS. FIGS. 2 to 5 show the embodiment shown in FIG.
FIG. 9 is an explanatory diagram showing an example of a conversion table when allocating a plurality of m spreading codes from a plurality of n spreading code candidates based on a data string of a second system and selecting one spreading code from among them. . Also, the spreading code length n shows the case where the assigned candidate has the same value. An orthogonal code is used as a spreading code candidate. Therefore, when the code length n = 8, there are eight spreading code candidates. As an example of the orthogonal code, the hierarchical orthogonal code described with reference to FIGS. 13 and 14 is used, but other orthogonal codes may be used.

FIG. 2 shows that one user has a spreading code length n = 16.
FIG. 6 is an explanatory diagram of a conversion table when one of all spreading code candidates is selected. According to 4 bits of input data of the second system, m = 16 spreading codes are allocated. Since all 16 spreading codes are assigned to one user, the second
One spreading code is selected for every three bits of the data string of the system. In the prior art, the spreading code is not changed by the input data. Therefore, in the embodiment of the present invention, by selecting one spreading code, it is possible to transmit as much as four bits of data as data of the second system per symbol.

Here, the symbol of the information modulation is composed of an I component in phase with the reference frequency signal and a Q component orthogonal to the reference frequency signal in multi-level modulation equal to or higher than QPSK modulation. Therefore,
Such processing for selecting a spreading code can be performed independently for each of the I-phase component and the Q-phase component.
That is, spreading codes can be assigned independently, and 4 + 4 =
More data can be transmitted by 8 bits. Regarding information modulation, when the same QPSK as in the past is used, two bits are processed per symbol of the data string of the first system by the information modulation. Therefore, in the prior art, only 2 bits could be transmitted per symbol, but when the spreading code candidate of FIG. 2 is used, 4+
4 + 2 = 10 bits can be processed and transmitted. That is,
10/16 = 0.625 bits are transmitted per chip. In the encoding unit 1, the encoding rate = 1,
That is, the transmission rate is described assuming that the encoding unit 1 does not perform encoding. Note that the chip rate is set to the same value as in the related art.

FIG. 3 is an explanatory diagram of a conversion table in a case where one user selects one of all spreading code candidates with a spreading code length n = 8. M = 8 spreading codes are allocated according to 3 bits of the data string of the second system. Therefore, more data can be transmitted by 3 bits per symbol. Spreading codes are independently assigned to the I component and the Q component,
In addition, when QPSK is used as information modulation, 3 + 3 + 2 = 8 bits can be transmitted per symbol. That is, 8/8 = 1 bit is transmitted per chip.

FIG. 4 is an explanatory diagram of a conversion table when two users select one out of four spreading code candidates with a spreading code length of 8, respectively. For example, in a base station,
When transmitting to a plurality of mobile station users who transmit simultaneously, or when receiving from a plurality of mobile station users who receive simultaneously, spreading code candidates having a code length n are assigned to the plurality of users. There are eight spreading code candidates with a spreading code length n = 8, which are divided into two and assigned to two users. In order to discriminate two users by the spread spectrum signal, each user uses different m = 4 spreading code candidates. As a result, in each user, one spreading code is selected for every two bits of the data string of the second system, and
One of m = 4 spreading codes is selected according to the bit. Therefore, each user can transmit more data by 2 bits per symbol.
When spreading codes are independently assigned to the I and Q components and QPSK is employed as information modulation,
2 + 2 + 2 = 6 bits can be transmitted or received per symbol. That is, 6/8 = 0.
75 bits are transmitted. When the number of users is further increased, when the spreading code length n is 8, eight users becomes the maximum number of users. In the case of the maximum number of users, as in the conventional example, only one spreading code is allocated, so that there is no data string of the second system. New code length n
For a user who has requested the assignment of a spreading code candidate of
A predetermined number of spreading code candidates that have not been allocated to other users have been allocated among the spreading code candidates having the code length n.

FIG. 5 shows a case where one user selects one of all spreading code candidates with a spreading code length n = 4 and a case where one user selects one of all spreading code candidates with a spreading code length n = 2. FIG. 4 is an explanatory diagram of a conversion table. In FIG. 5A, the second
M = 4 spreading codes are assigned according to 2 bits of the data string of the system. Therefore, more data can be transmitted by 2 bits per symbol. When a spreading code is independently assigned to the I component and the Q component, and QPSK is employed as information modulation,
2 + 2 + 2 = 6 bits can be transmitted. That is, 6/4 = 1.5 bits are transmitted per chip. In FIG. 5B, m = 2 spreading codes are assigned according to one bit of the data string of the second system. Therefore, more data can be transmitted by one bit per symbol. When spreading codes are independently assigned to the I component and the Q component and QPSK is employed as information modulation, 1 + 1 + 2 = 4 bits can be transmitted per symbol. That is, 4/2 = 2 bits are transmitted per chip.

FIG. 6 shows the result of studying each code length n with reference to FIGS. 2, 3 and 5 described above, limited to a case where one user selects one of all spreading code candidates. FIG. FIGS. 6A to 6D show spread codes having a code length n = 16, 8, 4, and 2, respectively. FIG. 6E is an explanatory diagram of the number of transmission bits per symbol and the number of bits per chip at each spreading code length n. In FIG. 6E, numerical values in parentheses are values in the related art. Although the number of bits that can be transmitted per chip is larger than that of the conventional technology, the longer the spreading code length, the larger the difference in the number of transmission bits between the two. Generally, in a case where m out of n spreading code candidates having a spreading code length n are assigned and one code is selected according to the data stream of the second system,
The number of transmission bits per chip is QPSK as information modulation.
And if no encoding is performed, 2 (log ₂ m +
1) / n.

To change the bit rate on the assumption that the chip rate is fixed, a plurality of methods can be adopted. (1) To increase the bit rate, the symbol rate may be increased, and for this purpose, the spreading code length n is shortened. (2) To reduce the bit rate, decrease the value of m. In the block diagram shown in FIG. 1, the bit rate can be made variable by combining the above two methods.

On the other hand, the bit rate can be increased simply by increasing the number of multiplexed spreading codes as in the prior art described above. Therefore, the first embodiment described above may be used for each system of spread code multiplexing. However, in the prior art, since the selection of the spreading code itself is not used for data transmission, the following method can be adopted as the second embodiment of the present invention. (3) To increase the bit rate, k spread codes are selected from m allocated spread codes and are used in parallel at the same time, and the user data is corresponded to the combination of the k spread codes. Let it. In the first embodiment, k = 1 spreading codes can be selected from m spreading codes and can be regarded as being used in parallel at the same time. This is an embodiment.

Description will be made using specific numerical values. (A) When a combination of k = 2 spreading codes is selected and used according to the second data sequence using all spreading code candidates m = 8 having a spreading code length n = 8, _m C _k = ₈ C ₂ = 28
You can select the street. As a result, data of log ₂ 28 ≒ 4.8 bits can be transmitted per symbol by selecting a spreading code, and spreading modulation can be performed independently for the I phase component and the Q phase component of information modulation. Therefore, twice as much data can be transmitted as the second data string. When QPSK is used as quadrature modulation, a 2-bit data stream of the first system can be spread-modulated for each spreading code.
= Data of 4 bits can be transmitted. Therefore, in total, 2k + log per symbol
₂ ( _{mC k} ) ≒ 4 + 4.8 = 8.8 bits of data can be transmitted. Per chip, 1 / n
(= 1/8) bits can be transmitted.

(B) A case where a combination of k = 3 spreading codes is selected and used according to the second data string using all spreading code candidates m = 8 having a spreading code length n = 8. , ₈ C ₃
= 56 different spreading codes can be selected, and 2k + log ₂ ( _m C _k ) = 6 + log ₂ 56 ≒ 11.8 per symbol.
Bit data can be transmitted, and 11.8 / n = 1.475 bits can be transmitted per chip. In the receiver shown in FIG.
Determines from the output of a plurality of despreading units 9 ₁ to 9 _m, by detecting the k outputs for outputting a peak value at the same timing, the spreading code combined in parallel. The information generating unit 12 calculates the k spreading codes shown in FIG.
In the transmitter of (b), data that matches the data of the second stream used for selecting the spreading code is generated. In the above description, the value of k is the same value for the I-phase component and the Q-phase component of the information modulation, but it is also possible to set each independently.

The transmission rate can be varied by combining the above first to third methods. Also in this embodiment, the information modulation method is not particularly limited. BP
The case of only the I phase like SK may be used. In the spread modulation, the spread modulation was performed independently for the I phase and the Q phase.
The I and Q phases may be spread using the same spreading code. The method of transmitting user data by a combination of a plurality of spreading codes is conventionally known as a "parallel combination spread spectrum communication system", but usable spreading code candidates are fixed and the transmission rate is fixed. Is not intended to be variable.

Also in the second embodiment, the transmission rate (or the transmission rate and the number of users), the spreading code length n of the spreading code candidate to be used, the number m of spreading code candidates allocated, and the spreading code used in parallel Is not necessarily one-to-one, the correspondence table or the like is prepared, and only by transmitting the rate information data (or the rate information data and the number of users), m spreads are performed. Either the code candidate and the value of k are set, or some control information for setting the m spread code candidates and the value of k is transmitted from the transmitting side. Alternatively, the transmission rate (or the transmission rate and the number of users) or each numerical value is determined on the receiver side, and the rate information data (or the rate information data and the number of users) or the control information described above is transmitted to the transmitter side. The transmitting side may set each spreading code candidate and the value of k according to the received rate information data (or the rate information data and the number of users).

In the above description, it has been described on the assumption that spreading code candidates having different spreading code lengths n are not used simultaneously. FIG.
As described with reference to, even if the spreading code lengths n are different, those having an orthogonal relationship can be selected. Thus, the transmission rate can be changed by combining codes having different spreading code lengths.
Also, in the information modulation section 4, the transmission rate can be changed even if the modulation multi-level number is changed.

As described above, according to the first embodiment of the present invention, as a result, the transmission rate can be increased as compared with the prior art. However, since the spread code length can be made longer than the conventional one, it is not limited to the advantage of the transmission amount, so that the processing capability for multipath is also improved. FIG. 7 is an explanatory diagram of the relationship between the multipath and the spreading code used in the first embodiment of the present invention. In the figure, the horizontal axis represents time, and the vertical axis represents relative received power. In the same propagation path as the multipath propagation path described with reference to FIG. 16, a spreading code of code length 8 is shown, with the spreading code cycle being adjusted to the time on the horizontal axis. Let us consider a case where transmission is performed at the same bit rate as the conventional one (one bit per chip). In this assumption, the four-symbol length of the prior art corresponds to one symbol length in the embodiment of the present invention. Therefore,
In the case of the embodiment of the present invention, all of the delayed waves 1 to 3 are included within one symbol length. On the other hand, in the related art described with reference to FIG.
3 exceeds one symbol length. Therefore, each of the delayed waves 1 to 3 becomes an interference signal unless separation using a long code or the like whose description is omitted is performed.

As described with reference to FIG. 16 (c), when code multiplexing is performed by the conventional technique, the spread code multiplexing is performed using four spreading codes, thereby achieving the first aspect of the present invention. As in the embodiment, all the delayed waves 1 to 3 do not exceed one symbol length. However, according to the embodiment of the present invention, transmission can be performed at the same bit rate as in the related art without performing spreading code multiplexing, so that the number of cross-correlations that need to be considered is reduced as compared with the related art. That is, the embodiment of the present invention requires an interference canceling circuit having a smaller scale than that of the related art.

Similarly, an interference canceling circuit such as a cross-correlation due to a delayed wave of another user in a downlink, a cross-correlation due to a loop of a transmission signal of another cell, and a cross-correlation by an asynchronous user in an uplink is also described in the present invention. In the first embodiment, the number of transmitted spreading codes can be reduced, so that the number is simplified.

In the second embodiment of the present invention, the first
When transmitting at the same bit rate as in the embodiment of
One symbol length can be further increased. In this case, since a plurality of codes are used in parallel, the amount of interference due to cross-correlation increases. Nevertheless, the number of cross-correlations that need to be taken into account when canceling interference is reduced, so that an interference canceling circuit having a smaller scale than the prior art is sufficient.

In the above description, the values of n, m, and k can be changed to make the transmission rate variable.
However, the change of the numerical values of n, m, and k described above can also be performed to achieve a purpose other than the change of the transmission rate. That is, even if the transmission rate is fixed, there are a plurality of combinations of the above numerical values. These multiple combinations have different numbers of users and transmission characteristics that can be used simultaneously, even if the transmission rates are the same.

In the third embodiment of the present invention, according to transmission accuracy required for transmission data, and / or the number of users to which the spreading code candidates are assigned, and / or propagation path conditions, A combination of the above numerical values is selected. As a result, it is not only controlled according to the transmission rate, but also the transmission accuracy required for transmission data, and / or the number of users to which the spreading code candidate is allocated, and / or adapted to the state of the propagation path It can be controlled to a mode of spread spectrum.

The accuracy of transmission required for transmission data is as follows:
It is represented by a transmission error rate or the like allowed for transmission data, and is related to the service type or medium of the transmission data. For example, audio data does not require much accuracy, but computer processing data requires accuracy.
Therefore, it can also be automatically determined according to the service type of transmission data or the media (for example, audio data, computer processing data, still image data, moving image data). In the case of transmission data requiring accuracy under the condition of a constant transmission rate, for example, the above-mentioned n may be large, k may be small, and m may be large. Also, the number m of spreading code candidates to be assigned must be reduced as the number of users using spreading code candidates having the same code length n increases so that transmission and reception can be performed for each user. Therefore, the mode of spreading is controlled according to the number of users. The condition of the propagation path is defined as the level of the received signal at the receiver (in addition to the level of the received signal from the transmitter,
It may be a level of a signal received from another transmitter), an interference wave level, a delay time of a delayed wave, or the like. When the condition of the propagation path is poor under the condition of a constant transmission rate, for example, the value of n may be large, the value of k may be small, and the value of m may be large.

The block diagram of this embodiment is not shown. However, in FIG. 1, “rate information data” may be replaced with the above-described conditions and used as information for setting the values of n, m, and k. A correspondence table between the above conditions and the above numerical values may be prepared in advance. Also in this case, the transmitting side transmits m spread code candidates of code length n and control information for controlling the value of k from the transmitting side of the spread spectrum signal to the receiving side, or conversely, The received control information may be transmitted from the receiver to the transmitter. When the transmitting side or the receiving side is a base station, the base station may control the spread spectrum mode of the mobile station.

FIG. 8 is an explanatory diagram of a combination example of the spreading code length n at which the transmission rates are equal, the number m of spreading code candidates to be allocated, and k which is the number of spreading codes used in parallel. FIG. 8A shows that one user is assigned m = 8 = 2 ³ candidates among spreading code candidates with a spreading code length n = 16,
A case is shown in which one spreading code is selected according to the second data string. When QPSK is used as information modulation, the number of data bits per symbol is 3 + 3 + 2 =
This is 8 bits, 0.5 bits per chip.
FIG. 8 (b), one user of the spreading code candidates of the spreading code length 8, m = 2 = 2 ¹ candidate is assigned, from among them, depending one spreading code to the second data sequence Shows the case of selecting. When QPSK is used as information modulation, 1
The number of data bits per symbol is 1 + 1 + 2 = 4 bits, which is 0.5 bit per chip. Therefore, the transmission rates of both FIGS. 8A and 8B are equal. However, from the viewpoint of the spreading gain (the number of chips per symbol), the case of FIG.
On the other hand, in the case of FIG. Therefore, the accuracy of the transmission is better in FIG. On the other hand, from the viewpoint of the number of users that can transmit simultaneously, in the case of FIG. 8A, only two users can be stopped, whereas in the case of FIG. 8B, four users can be allocated.

Next, the first embodiment described with reference to FIG. 1 is applied to a CDMA communication system using a plurality of subcarriers, for example, OFDM (Orthogonal Frequency-Division Mu).
The case where the present invention is applied to the configuration of the spread spectrum signal generation unit for each subcarrier of (ltiplexing) will be described with reference to FIGS. The total number of subcarriers is s. The second embodiment in which a combination of a plurality of spreading codes is used for data transmission, and the third embodiment in which a combination other than the purpose of making the transmission rate variable, can be similarly applied.

FIG. 9 is a block diagram of a transmitter in the spread spectrum communication system according to the fourth embodiment of the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals. Reference numeral 21 denotes a distribution unit. Reference numeral 22 denotes a spread spectrum signal generation unit, which has the same configuration for each subcarrier. However, in the subcarrier 1 block, a rate information insertion unit 23 is provided. 24 is an inverse fast Fourier transform processing unit, 25 is a parallel / serial conversion unit, and 26 is a guard insertion unit. Although illustration is omitted,
For each subcarrier, a pilot signal for fading distortion compensation is inserted into user data and inverse fast Fourier transformed. Reference numeral 27 denotes a wireless circuit unit, which has the same configuration as the wireless circuit unit 7 in FIG.

The input data is distributed by the distributor 21 to the channels of the subcarriers 1 to s of the spread spectrum signal generator 22. The rate information data is inserted for each frame in the rate information insertion unit 23 provided in the subcarrier 1. In addition, since each frequency band is the same, in all the channels of subcarriers 1 to s,
Information modulator 4, spread code number selector 5, and spreader 6
Is predetermined by the rate information data,
A common information modulation speed (symbol rate; determined by the spreading code length n because the chip rate is fixed), a common spreading code candidate allocation number m (in the second embodiment, a common parallel use is further performed). It can be processed by the number k) of spreading codes. Therefore, each subcarrier 1 to
There is no need to add rate information data for each s.

Subcarrier 1 processed in this way
The spread-spectrum signal for each 〜s is converted to a time signal by an inverse fast Fourier transform (inverse FFT) processing unit 24. The signal after the inverse fast Fourier transform processing is converted into a serial signal by the parallel / serial conversion unit 25, a guard interval is inserted in the guard insertion unit 26, and the signal is transmitted through the radio circuit unit 27. Note that the guard interval is set in the latter half of each processing unit (1 FFT symbol) of the inverse FFT.
This is a process of adding data for t / N time to the head of one processing unit. Here, the constant t indicates one FFT symbol period,
The constant N is a real number with 1 <N. MMAC (Multimedia Mobile A
ccess Communication system), a value of about N = 10 is used. On the receiving side, this guard interval prevents the delayed wave from entering the subsequent inverse FFT processing unit and causing interference. Also,
Since the guard interval uses a part of its own signal, the frequency component is the same as the original, and the influence of the insertion is small.

FIG. 10 is a block diagram of a receiver in a spread spectrum communication system according to a fourth embodiment of the present invention. In the figure, reference numeral 31 denotes a wireless circuit unit,
Has the same configuration as that of the wireless circuit section 8. 32 is a guard removing unit, 33 is a serial / parallel conversion processing unit, 34 is a fast Fourier transform processing unit, and 35 is a rate information determination unit.

The received signal becomes a baseband signal in the radio circuit section 31. After the guard interval is removed by the guard removing unit 32, the serial / parallel conversion processing unit 33
Then, a conversion process to a parallel signal is performed. Then, the signal is converted into a signal for each subcarrier by the fast Fourier transform processing unit 34. Despreader 9 ₁ to 9 _m, comparator unit 10, information demodulation section 1
1, the information generation unit 12 is the same as that of FIG. 1, and the same configuration is provided for each of the subcarriers 1 to s. Reference numeral 36 denotes a fading distortion compensator provided for each of the subcarriers 1 to s. For example, a pilot signal inserted on the transmission side for each of the subcarriers 1 to s is extracted and received by fading. The phase fluctuation and the amplitude fluctuation of the signal are estimated to compensate for the fading distortion received by the received signal.

On the transmitting side, the rate information data inserted into the spread spectrum signal of subcarrier 1 is determined by the rate determination section 35 of subcarrier 1 and the despreading sections 9 _{1 to} 9 _{m of} each of subcarriers 1 to s are determined. Are performed. 3
Reference numeral 7 denotes a reconstructing unit that outputs reconstructed output data of the output data of all the subcarriers 1 to s. The reconstructing unit 37 may use the rate information data obtained by the rate information determining unit 35 in some cases.

FIG. 11 is an explanatory diagram of a signal format including rate information data according to the fourth embodiment of the present invention shown in FIGS. FIG. 11 (a), FIG.
(B) shows two specific examples. In each example, the relationship between transmission data and rate information data is shown for each of the subcarriers 1 to s. In FIG. 11A, rate information data is inserted only into the channel of subcarrier 1 for each FFT symbol period.
On the other hand, in FIG. 11B, in each of the subcarriers 1 to s, the rate information data is inserted in the data sequence for each 1FFT symbol period. Each subcarrier 1
When the same transmission rate is used for channels の to s, use of the transmission format of FIG. 11A eliminates the need to send rate information for each subcarrier.
The apparatus can be simplified. Different transmission rates can be used for each sub-channel, in which case
What is necessary is just to transmit by the transmission format of FIG.11 (b). Note that the above-described rate information data is merely an example, and may be replaced with the control information described in the first to third embodiments. As described above, as the fourth embodiment,
A CDMA communication system using multiple subcarriers has been described. There is also a CDMA communication system using a plurality of carriers. In this system, the channel configuration of each subcarrier in FIGS.
What is necessary is just to employ | adopt as a structure of the channel of s.

The spread spectrum communication system according to the present invention can also be implemented as a combination of the conventional spread spectrum communication method. That is, when the conventional spread spectrum communication method is followed, the transmission data is not distributed for selecting the spread code. The selected spreading code does not change depending on the information of the transmission data of the user, but is changed only by changing the transmission rate or the like according to the conventional control method. Even when performing spread code multiplexing by the control method of the related art, the selected plurality of spread codes does not change depending on the information of the transmission data of the user.

Specifically, when the conventional spread spectrum communication method is followed, the transmission data is directly or distributed to form first to k-th (k is an integer of 1 or more) data strings, and the first to k-th data strings are transmitted. Are respectively modulated, and m = k spread code candidates are assigned and selected from spread code candidates having a code length n (n is an integer of 2 or more),
Using the selected k spreading codes, spread the information modulated first to k th data sequences, transmit the spread as a spread spectrum signal, receive the spread spectrum signal, and obtain the m = k spread spectrum signals. Despreading the spread-spectrum signal using the spread code and demodulating the despread output to output the first to k-th data strings, and outputting the first to k-th data strings. The data sequence is used as it is or reconstructed as reception data.
= K is variably controlled according to the transmission rate required for the transmission data.

Whether to follow the spread spectrum communication system according to the present invention or the spread spectrum communication method of the prior art is determined by assigning a transmission rate required for transmission data, transmission accuracy required for transmission data, and a spreading code candidate. Switching may be performed according to at least one condition such as the number of users to be used and the state of the propagation path. Alternatively, when one of the devices on the transmitting side and the receiving side is a device that can only support the spread spectrum communication method of the related art, the other device does not follow the spread spectrum communication system according to the present invention, and You may make it follow the spread spectrum communication method of technology.

[0072]

As is apparent from the above description, the present invention has the effect of reducing the number of multiplexed codes when performing high-speed transmission. By suppressing the chip rate of the spread code at the time of high-speed transmission to a low speed, it is possible to reduce a multipath exceeding a code cycle and to suppress an increase in a circuit scale of a circuit for removing interference caused by the own multipath. As a result, communication at various transmission rates from high-speed data to low-speed data can be processed with a small number of spread code multiplexes and a low chip rate. As a result, the symbol period can be lengthened and the transmission efficiency is good, so that multipath interference due to a long-cycle delayed wave exceeding the symbol period can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conversion table when one user selects one of all spreading code candidates with a spreading code length n = 16.

FIG. 3 is an explanatory diagram of a conversion table when one user selects one of all spreading code candidates with a spreading code length n = 8.

FIG. 4 is an explanatory diagram of a conversion table in a case where two users each select one out of four spreading code candidates having a spreading code length of 8;

FIG. 5 is a conversion table in a case where one user selects one of all spreading code candidates with a spreading code length n = 4, and in a case where one user selects one of all spreading code candidates with a spreading code length n = 2. FIG.

FIG. 6 shows a result of studying each code length n with reference to FIG. 2, FIG. 3, and FIG.
FIG. 9 is an explanatory diagram summarizing only when the number is selected.

FIG. 7 is an explanatory diagram of a relationship between a multipath and a spreading code used in the first embodiment of the present invention.

FIG. 8 is an explanatory diagram of an example of a combination of a spreading code length n at which the transmission rates are equal, a number m of spreading code candidates to be allocated, and a number k of spreading codes used in parallel.

FIG. 9 is a block diagram of a transmitter in a spread spectrum communication system.

FIG. 10 is a block diagram of a receiver according to a fourth embodiment of the present invention.

FIG. 11 is an explanatory diagram of a signal format including rate information data in the form of the block configuration diagrams shown in FIGS. 9 and 10;

FIG. 12 is a block diagram of a conventional spread spectrum communication system.

FIG. 13 is an explanatory diagram of a spreading code used in the conventional spread spectrum communication system shown in FIG.

14 is an explanatory diagram of the code generation principle of the spread code shown in FIG.

15 is an explanatory diagram of an example of the auto-correlation and cross-correlation of the spreading code shown in FIG.

FIG. 16 shows a multipath in a multipath propagation path and FIG.
FIG. 4 is an explanatory diagram of a relationship with a conventional spreading code shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Encoding part, 2 ... Interleave part, 3 ... Distribution part, 4 ...
Information modulation section, 5 spreading code selection section, 6 spreading section, 7 radio circuit section, 8 radio circuit section, 9 despreading section, 10 comparison section, 11 information demodulation section, 12 information generation section , 13: Reconstruction unit, 14: Deinterleave unit, 15: Decoding unit

Claims (1)

[Claims] 1. A spread spectrum communication method for receiving a spread spectrum signal on a plurality of channels and receiving the spread spectrum signals of the plurality of channels as signals of different carriers or different subcarriers. Are transmitted to the first to (k + 1) (k)
Is distributed to a data string of 1 or more integers, and has a code length n (n
Are m (m is an integer of 2 or more) spread code candidates assigned from (2 or more integers) spread code candidates, and k spread codes are selected according to the (k + 1) -th data sequence. By using the selected and selected k spreading codes, a signal information-modulated by the first to the k-th data sequence is spread to obtain a spread spectrum signal of the plurality of channels, While receiving signals transmitted as spread spectrum signals of a plurality of channels as signals of different carriers or different subcarriers, respectively, m spread code candidates having a code length n inserted into one of the channels, and receiving control information for controlling the value of k as common to each of the channels; and receiving the spectrum for each of the channels. Despreading the spread signal using the m spread code candidates; and specifying the k spread codes selected at the time of transmission based on the despread output, thereby obtaining the (k + 1) th spread code. Outputting the data sequence; outputting the first to k-th data sequences by demodulating the information of the despread output using the identified k spreading codes; Reconstructing the first to k-th data strings and the (k + 1) -th data string for the plurality of channels to be reception data; and at least one of the n, m, and k values is: Variably controlling according to the control information as a value common to each of the channels.