JPH10190614A - Spread spectrum transmitting method, and transmission and reception device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the spread spectrum transmitting method which enables high-speed transmission of sufficient transmission quality even in complicated radio wave propagation environment. SOLUTION: A transmit information signal I is spread by spread spectrum part 1 with a spread spectrum code C to output a spectrum spread signal SS, and a time-base replacement part 3 replaces the signal by chip sections along the time base according to a time-base replacement code outputted from a time-base replacement code memory 4 to output a signal TS which is made random along the time base. This signal TS is further converted by a frequency conversion part 5 to a proper frequency, amplified by a power amplifier 6, and radiated as a radio wave from an antenna 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum transmission method, a spread spectrum transmission transmitter, and a spread spectrum transmission receiver.

[0002]

2. Description of the Related Art FIG. 6 is a schematic block diagram of a spread block in a conventional CDMA spread spectrum transmission method. FIG.
7 is a signal waveform diagram for describing an operation example of the spread transmission method shown in FIG. In the figure, reference numeral 17 denotes an adder. In the field of mobile communications, CDMA (Code Division)
On Multiple Access (code division multiplexing) spread-spectrum transmission methods are receiving attention. In the conventional spread spectrum transmission method, spread modulation is performed on amplitude or frequency using a spread code. In the example shown in FIG. 6, spread modulation is performed on amplitude. Information signal X
The spread modulation is performed by adding the spread code Y and the spread code Y by an adder 17 (exclusive OR circuit).

As shown in FIG. 7, the result of diffusion is (X
+ Y) = Z (mod2). In the drawings, a regular symbol representing an exclusive OR is used. However, since this symbol cannot be used in the specification, the addition in parentheses such as (X + Y) represents the exclusive OR.
As a spread signal Z, for example, for a 1-bit section in which the information signal X represents “1”, when viewed for each chip section,
Z1, Z2, Z3, Z4, Z5,... = “00101
... ". When the spread signal Z obtained here is transmitted through a multipath transmission path, interference occurs due to variations in delay time between the paths, and it is difficult to ensure sufficient transmission quality. become. In particular, in a propagation environment in which the reception electric field changes greatly with time due to fading and the electric field intensity is extremely reduced, the reception quality is greatly deteriorated, which is a serious problem.

FIG. 8 is a waveform diagram for explaining an example of multipath reception. In the spread signal Z that should be received,
Due to the multipath, the interference wave signals R are relatively delayed by τ1 to τN, respectively, and have different amplitudes.
A signal in which Z1 to RZN are combined is received. However, in a propagation environment in which electric field fluctuation due to fading is severe, it becomes difficult for the receiver to perform normal reception.

Conventionally, as a countermeasure, a method of removing an interference wave using an adaptive antenna or performing a rake reception has been used. However, when an adaptive antenna is used, the function of detecting an incoming wave is complicated and large, and is not suitable for miniaturization of a portable device. When used in a base station, the arrival angle difference between the desired wave and the interference wave is not always sufficient, so that the desired wave and the interference wave cannot always be easily distinguished. Further, there is a problem that an interference wave received from the same direction as the desired wave cannot be removed.

On the other hand, in the case of RAKE reception, a method is used in which a received signal is input to a delay circuit, a plurality of outputs of the delay circuit are appropriately weighted, and they are added and output. In this case, an algorithm for calculating the delay amount of the delay circuit and a calculation algorithm for weighting each output are complicated in order to process a complicated multipath phenomenon. Furthermore, since the processing time increases when the multipath is complicated, there are cases where the processing cannot be performed particularly when moving in a complicated service area at high speed. In the case of high-speed transmission, there is a limit to the amount of delay that can be made by the delay circuit, so that it may not be possible to process when the delay time difference between the paths is too large. For example, when the delay time difference between paths is 10 μsec, the
For high-speed transmission of about bps, one bit (= 0.1
μsec is assumed to be 10 taps using a delay element of 10 taps.
A delay circuit of μsec / (0.1 μsec / 10) = 1000 taps is required, which is not easy to realize.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and achieves high-speed transmission with sufficient transmission quality to a high-speed moving object even in a complicated radio wave propagation environment. It is an object of the present invention to provide a spread spectrum transmission method, a spread spectrum transmission transmitter, and a spread spectrum transmission receiver that are enabled.

In the case where the propagation path is multi-path, in order to realize high-speed transmission with high quality, interference due to delay between the paths and fluctuation of the received electric field become problems. The present invention is particularly effective in such a case. The present invention can easily remove an interference wave with a simpler configuration than the conventional technology, and also improves the reception quality by time diversity in "bit units" of an information signal.

[0009]

According to the first aspect of the present invention, in the spread spectrum transmission method, an information signal is spread spectrum by a spread code, and an arrangement order of the spread signal on a time axis is determined by the spread code. It is exchanged according to a predetermined rule with the chip section as a unit and transmitted,
Arrangement order on the time axis of the received signal is replaced by a rule opposite to the predetermined rule in units of the chip section,
The spectrum is despread with respect to the exchanged signal, and the information signal is identified for each bit section of the information signal based on the despread output. Therefore,
The interference wave removal and time diversity functions can be realized with a simple configuration.

According to a second aspect of the present invention, in the spread spectrum transmission method according to the first aspect, the predetermined rule randomly changes an arrangement order of the spread signal on a time axis using a random number. Things. Therefore, even if the spread spectrum code C is relatively simple, the irregularity in the radio transmission section becomes large,
Sufficient characteristics are easily obtained for spectrum diffusion. In addition, when the time axis is reversed, the interference wave components are likely to be uncorrelated. For example, since signals in the chip section within the same symbol are not periodically distributed,
It does not coincide with the periodic fading period.

In the invention according to claim 3, in the spread spectrum transmission method according to claim 1, the predetermined rule is that the n-th bit section of the bit section corresponding to the m-th symbol of the information signal. When the spread signal in the chip section is Smn and the output after replacement in the nth chip section of the bit section corresponding to the mth symbol of the information signal is Tmn, Tm
It is replaced so that n = Snm.

Therefore, as a result of the rearrangement, there is no possibility that the signals in the chip section in the same symbol converge to the adjacent or nearby area, and the effect of time diversity is expected to be uniformly improved for any symbol of the information signal. Also,
There is an advantage that the time axis can be switched with a simple algorithm, and the line test can be easily performed because the time axis switching algorithm is easy to understand.

According to a fourth aspect of the present invention, in the spread spectrum transmission method according to any one of the first to third aspects, the information signal is transmitted as a packet, and the information signal is transmitted on the time axis. The range in which the arrangement order is exchanged is the entire range of the duration of the packet of the information signal. Therefore, the range of replacement of the time axis is the largest, and the effect of the time diversity is enhanced.

According to a fifth aspect of the present invention, in the transmission apparatus for spread spectrum transmission, first means for spreading an information signal by a spread code, and an arrangement order of outputs of the first means on a time axis. In accordance with a predetermined rule, and outputs the result by using the chip section of the spreading code as a unit. Therefore,
With a simple configuration, it is possible to obtain a transmission device for realizing the interference wave removal and time diversity functions.

According to a sixth aspect of the present invention, in the receiving apparatus for spread spectrum transmission, the arrangement order of the received signals on the time axis is switched according to a predetermined inverse conversion rule in units of chip sections of the spread code and output. A third means for performing spectrum despreading on an output of the third means, and the information for each predetermined bit section of the information signal based on an output of the fourth means. It has a fifth means for identifying a signal. Therefore,
With a simple configuration, it is possible to obtain a receiving device for realizing an interference wave removal and time diversity function.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a transmitting apparatus used in an embodiment of the CDMA radio transmission method according to the present invention. In the figure, 1 is a spread spectrum unit, 2 is a spread spectrum code memory, 3 is a time axis replacement code memory, 4 is a time axis replacement code memory, 5 is a frequency conversion unit, 6 is a power amplifier, and 7 is a transmission antenna. The transmission information signal I is spread in a spread spectrum unit 1 by a spread spectrum code C output from a spread spectrum code memory 2, where a spread spectrum signal SS is output.

The spread spectrum signal SS is replaced in the time axis switching section 3 in accordance with the time axis replacement code output from the time axis replacement code memory 4 for each chip section in the time axis direction. The rule of the replacement will be described later with reference to FIGS. here,
A signal TS randomized in the time axis direction is output.
The signal TS randomized in the time axis direction is further converted to an appropriate frequency by the frequency converter 5, amplified by the power amplifier 6, and emitted from the antenna 7 as a radio wave.

FIG. 2 is a block diagram of a receiving apparatus used in an embodiment of the CDMA radio transmission method according to the present invention. In the figure, 8 is a receiving antenna, 9 is a front end, 10 is A
/ D conversion unit, 11 is a time axis reverse permutation unit, 12 is a time axis reverse permutation code memory, 13 is a spectrum despreading unit,
14 is a spectrum despreading code memory, 15 is an average value acquisition unit, and 16 is an identification unit.

The high-frequency signal received by the receiving antenna 8 is converted by the front end 9 into an intermediate frequency band,
The signal is converted into a digital signal by the D conversion unit 10 and thereafter digitally processed. When the radio wave emitted from the transmitting device reaches the receiving device through complex multipath propagation, the output of the A / D converter 10 includes an interference wave component R in addition to the desired wave component TS to be originally received. Have been.
The interference wave component R in this case is generated by multipath propagation, and is, for example, a certain time τ compared to the desired wave component TS.
Just delayed.

The A / D converter 10 generates a desired wave component TS
Then, the interference wave component R is digitized thereafter, so that the processing in the subsequent time axis reverse switching unit 11 is simplified. In the time axis reverse permutation unit 11, the time before the time axis permutation is performed by the time axis permutation unit 3 of the transmitting apparatus shown in FIG. 1 according to the time axis reverse permutation code output from the time axis reverse permutation code memory 12. It is returned to the array order on the axis. That is, when there is no interference wave component R, the time axis reverse permutation unit output SR shows the same signal state as the spread spectrum signal SS in the transmission device.

The time axis reverse switching unit 11 performs processing in synchronization with the time switching unit on the transmitting apparatus side shown in FIG. Synchronization systems such as chip synchronization, bit synchronization, and synchronization of time axis switching are separate technologies, and description thereof is omitted, but a synchronization detection unit can be provided in the front end 9. Regarding the synchronization of time swapping, for example, the transmitting device first transmits a synchronization signal in a state where time swapping is not performed, and the receiving device detects this synchronization signal and performs correlation detection, and then reverses the time axis. May be started.
Further, even during the time reverse operation, it is possible to always control the synchronization of the time axis reverse exchange while determining whether the result of the despreading is normal.

Next, the output SR of the time-axis reverse-swapping unit is despread by the spectrum despreading unit 13 using the spectrum despreading code C output from the spectrum despreading code memory 14. Here, the average value of the signal SRC obtained by despreading is calculated by the average value acquisition unit 15. Further, the output MEAN is compared with a predetermined threshold value by the identification unit 16 and identified, and the received information signal J is identified.
Get. The reception information signal J matches the transmission information signal I when there is no error.

FIG. 3 is an explanatory diagram of a first specific example of replacement of spread spectrum signals by the transmitting apparatus shown in FIG. The correspondence relationship in the time axis direction among the transmission information signal I, the spread spectrum code C, the spread spectrum unit output SS, and the time axis replacement unit output TS is shown, but the time delay required for processing is ignored. . For the sake of simplicity, here, the transmission information signal I shown in FIG. 1 is described as binary “0” and “1”,
Similarly, the spread spectrum code C and the time axis replacement code are also binary “0” and “1”.
In the description, it is assumed that the addition by mod2 is performed.

In this specific example, the time axis switching unit 3 shown in FIG. 1 uses a rule in which the chip section (Tc) is replaced in the time axis direction as a unit. The order is changed.

Transmission information signal I and spread spectrum code C
Is added by mod2, and the output S of the spread spectrum unit is obtained.
S has been obtained. In this case, the transmission information signal I is represented as I1, I2, I3, Im,... For each bit section (TI). On the other hand, the spread spectrum code C is made to correspond to each transmission information signal Im, and is further divided into chip sections (Tc) and represented by Cmn. Therefore,
The output SS of the spread spectrum unit is Smn = (Im + Cm
n). Here, Cmn is P
A random signal having a small autocorrelation such as an N signal (pseudo-random signal) is suitable, and its cycle is selected to be longer than the delay time difference expected in multipath propagation.
At the spread spectrum section output SS, as a result of mod2 addition, the frequency band is spread in accordance with the chip rate and spread in the frequency direction.

The output SS of the spread spectrum unit is
In the time axis exchange unit 3 shown in FIG. 1, the arrangement order is randomly exchanged for each chip in the time axis direction. In the illustrated example, S11 is the same time axis position,
S12 is replaced with another chip section of the same bit section,
S13 is replaced with the first chip section of the third bit section. Also, S23 of the second bit section is replaced with a second chip section of the first bit section, and the last S2N of the second bit section is replaced with a first chip of the second bit section. In this case, the replacement of the time axis is also performed for chips separated by a delay time difference or more expected by multipath propagation. The output TS of the time axis exchange unit generated in this manner is obtained by spreading in the frequency axis direction by the spread spectrum code C and further spreading in the time axis direction when viewed in chip units.

FIG. 4 is an explanatory diagram of a first concrete example of the despreading of the received signal corresponding to the first concrete example of the replacement of the spread spectrum signal shown in FIG. A / D conversion section output TS + R, time axis reverse exchange section output SR, spectrum despreading section output SRC, average value acquisition section output MEAN
Although the correspondence relationship in the time axis direction is shown, the time delay required for processing is ignored.

When viewed from the output of the A / D converter 10 shown in FIG. 2, the received signal includes, in addition to the desired wave component TS as the desired wave to be received, the interference wave of the delayed interference wave. Component R is included. Here, for simplicity,
As the interference wave component R, only one wave is used. Desired wave component T
The amplitude of the interference wave component R is different from that of S, and the interference wave component R is further delayed by a certain time τ. Here, Sm of desired wave component TS
The signal in the chip section of the interference wave component R corresponding to the signal in the n chip section is Rmn. Note that the desired wave component TS and the interference wave component R are both analog signals whose amplitudes fluctuate with time, and the output TS +
R is also multi-valued, but is represented here by "1" and "0" for simplicity.

The output of the A / D converter 10 shown in FIG.
The switching is performed by the time axis reverse switching unit 11 in exactly the reverse of the transmission. If there is no interference wave R, the output SR of the time axis reverse permutation unit matches the output SS of the spread spectrum unit in FIG. This time axis reverse swap is to try to return Smn to the original,
On the other hand, Rmn remains completely randomized.

For example, as a result of performing the time axis reverse swap,
S11, S12, S13,..., S1N represent the spectrum spread of I1, but R11, R1
2, R13,..., R1N are not correctly reversed because the ones shifted by the delay time τ are reversed in the time axis. That is, R11, R12, R
13,..., R1N are signals that are spread in the time axis direction by a certain time axis replacement code, and randomized in the time axis direction by another time axis reverse replacement code.

Next, in the spectrum despreading unit 13 shown in FIG. 2, despreading is performed using the same spreading code C as used when the spectrum of the transmission signal is spread. in this case,
(Smn + Cmn) = ((Im + Cmn) + Cmn) =
Since Im is satisfied, the output SRC of the spectrum despreading unit for each 1-bit section is (Sm1 + Cm1) + (Sm2 + Cm2) + ... + (SmN + CmN) + (Rm1 + Cm1) + (Rm2 + Cm2) + ... + (RmN + CmN) = N × Im + (Rm1 + Cm1) + (Rm2 + Cm2) +... + (RmN + CmN) (1)

Here, since Rmn and Cmn have an independent relationship, (Rmn + Cmn) is regarded as a random random variable, and (Rm1 + Cm1) + (Rm2 + Cm2)
+ ... + (RmN + CmN) has a binomial distribution centered on a certain value M.

Further, the average value acquisition unit 15 shown in FIG. 2 calculates the average value of the spectrum despreading unit output SRC expressed by the above equation (1) over a 1-bit section, and outputs the average value output MEAN. {N × Im + ((Rm1 + Cm1) + (Rm2 + Cm2) +... + (RmN + CmN)} / N = Im + {(Rm1 + Cm1) + (Rm2 + Cm2) +... + (RmN + CmN)} / N・ Output (2).

The discriminating section 16 outputs the output MEA of the average value acquiring section.
N is compared with a predetermined threshold to determine whether the symbol is 1 or 0, and outputs the determination result as a received information signal. In the above equation (2), when N becomes sufficiently large,
｛(Rm1 + Cm1) + (Rm2 + Cm2) +... +
Since the behavior of (RmN + CmN)｝ / N approaches the average value M, this change is smaller than the change of Im,
It is possible to identify whether the average value output MEAN is in the “0” state or the “1” state. Normal C
In DMA, the value of N is selected to be a sufficiently large value of about 10 to 100. Therefore, when the expression (2) is identified, the following expression is obtained.

Im + {(Rm1 + Cm1) + (Rm2 + Cm2) +... + (RmN + CmN)} / N {Im + M (constant) (3) From this result, the information signal is reproduced except for the constant M. Can be done easily.

Therefore, the interference wave component is removed in the process of performing the reverse time axis swapping, performing the spectrum despreading and calculating the average value. In the above description, it is assumed that the number of interference waves is one for simplicity. At the same time, the received S
Even if some of the signals of S11, S12, S13,..., S1N are erroneous, the effect becomes 1 / N, as can be seen from the process leading to equation (3). Note that the average value acquisition unit 15 merely divides by N in units of one bit section, and is not always necessary if the threshold value of the identification unit 16 is determined according to the value of N.

In an actual receiving apparatus, the amplitude of a received signal varies with time. In accordance with this change, the A / D converter 10
The digital value representing the amplitude of the output TS + R also changes. In this case, the output TS + R of the A / D converter 10 is
Instead of "1" and "0", it becomes a digital signal representing a positive / negative amplitude centered on 0.
As the spread spectrum code C, codes representing +1, -1 are used, and multiplication is performed in the spectrum despreading unit 13. However, substantially the same arithmetic processing as the above-described equation (1) is performed. In the process, it is understood that a component having a large absolute value of the amplitude, in other words, a component having a good signal quality is added as a large value, so that the reception quality is improved.

As is clear from the above description, the reception quality by time diversity is improved in "bit units" of the information signal. That is, in the wireless transmission path, one symbol of the transmission information signal I is finely divided in chip section units, which are the shortest pulse width units of the spreading code, and spread in the bit sections of other symbols, and spread in time. I have. Therefore, even if the state of the transmission path is bad for a certain period due to fading, noise, or the like, it is possible to reduce the influence on the entire bit of the transmission information signal I. , And the bit error rate of the received information signal is improved. Even if the quality of the wireless channel deteriorates only for a specific period due to fading, noise, or the like, the influence on the reproduced information signal can be reduced in “bit units”.

At this time, the time axis switching unit 3 shown in FIG.
In this case, the effect of the time spread of the exchange of signals in units of chip sections is wider as compared with the period in which the electric field strength is reduced or noise is added. The reason is that
The reason for this is that when the signals are separated in time, the correlation between signals in units of chip sections is easily made uncorrelated, and the time diversity effect is increased. Therefore, for example, when the transmission information signal I is a packet signal of about several tens of msec, the time axis is replaced using the entire duration of the packet so that the replacement range of the time axis is maximized. It is suitable.

Further, even a propagation path having a relatively large delay time difference can be easily processed. In the case of conventional RAKE reception, it is difficult to process an interference wave having a delay time difference of one symbol length or more. However, the embodiment of the present invention is not limited to the limitation. In addition, the hardware scale is small and suitable for miniaturization. Swap the time axis,
In addition, all of the reverse permutations can be processed in a digitized state, and can be implemented as an IC using a gate array or the like. A simple configuration and easy IC implementation means economical.

Since the transmitting device only has to change the time axis arrangement according to a predetermined time axis changing code and perform the reverse on the receiving device, the changing algorithm is simple, and the state of the propagation path is determined. Does not require complicated processing. Since there is no process for checking the state of the propagation path, processing can be performed in a short time, and the response characteristics are excellent.
The short processing time means that the present invention can be applied to a portable device that moves at high speed. On the other hand, in the case of the conventional adaptive antenna, an algorithm for examining an incoming wave is required, and a process for examining each delayed wave is also required for RAKE reception.

Further, according to the first specific example of the above-mentioned exchange, the time axis exchange section 3 of the transmitting apparatus shown in FIG.
In, a pseudo random number is used as a time axis exchange code, and the exchange is performed randomly. Therefore, even if the spread spectrum code C is relatively simple,
Irregularities in the wireless transmission section are increased, and sufficient characteristics are easily obtained for spectrum spreading.

Further, in the time axis reverse permutation unit 11 of the receiving apparatus shown in FIG. 4, when performing the time axis reverse permutation, Rmn and Rmk (n ≠ k) tend to be uncorrelated. Has the effect of being able to easily obtain the independence. As the independence increases, the degree of randomness of Rmn after the reverse swap of the time axis also increases. For example, since the signals in the chip section in the same symbol are not periodically distributed, they do not coincide with the period of the periodic fading. The random number used as the time axis replacement code has a periodicity because a pseudo random code is actually used. This cycle is desirably longer than the long cycle of fading.

In order to make Rmn and Rmk (n ≠ k) uncorrelated, a large spread spectrum code (for example, PN
In the case of a signal, it can be obtained even if the irregularity in the wireless transmission section is increased by using a signal having a higher order. in this case,
The change of the time axis can be performed by a relatively simple algorithm, and sufficient characteristics can be obtained with respect to the spread of the spectrum.

Although not a spread spectrum transmission technique, in a general technical field of communication transmission, a symbol sequence itself in which an error correction code having a high error correction capability of a discrete error is added to a symbol of transmission information has been conventionally used. There is a technique in which the data is exchanged on the time axis and transmitted, and the reception is reversely exchanged. In this method, even when the transmission quality is reduced over a period of a plurality of consecutive symbols, error correction is performed by changing an error mode so as to increase the interval between erroneous symbols. .

On the other hand, in the above-described rearrangement in spread spectrum transmission, rearrangement is performed not in units of symbol periods but in units of chip periods, and the reception side simply collects the original data again. It will be. Therefore, it is possible to perform the error correction independently of whether or not the error correction of the symbol is performed in the subsequent processing block on the receiving side. On the receiving side, the effect of interference waves and noise is removed in connection with the above-described spectrum despreading processing, which is unique to spread spectrum transmission technology.

FIG. 5 is an explanatory diagram of a second specific example of the replacement of the spread spectrum signal by the transmitting apparatus shown in FIG. The correspondence relationship in the time axis direction between the transmission information signal I, the spread spectrum unit output SS, and the time axis replacement unit output TS is shown, but the time delay required for processing is ignored. This specific example is based on the rule that the time axis switching unit 3 of the transmitting apparatus shown in FIG. 1 performs switching in the time axis direction on a chip section basis, as n rules of the section corresponding to the m-th bit of the transmission information signal. The signal of the eye section is transposed in a rectangular shape.

That is, with respect to the output SS of the spread spectrum unit, the n-th chip of the bit section corresponding to the m-th bit of the information signal is represented by Smn. The value of the section corresponding to the n-th chip is represented by Tmn. In the time axis exchanging unit 3, the transposition is performed such that Tmn = Snm. As a means for performing such transposition, for example, a memory that stores input information at two addresses of a row and a column is used. The input information may be sequentially written from the first row in row units, and the stored information may be sequentially read from the first column in column units.

In the spread spectrum unit 1, when one bit section of one symbol of the information signal is spread by the N-chip spreading code C, the output SS of the spread spectrum section is divided into N output signals in units of one chip section. However, these are allocated to a plurality of bit sections in the time axis switching unit 3, and the information of each original symbol is equally allocated to the time domain of each N bit section. FIG.
In FIG. 5, for simplicity of illustration, the number of chips is replaced in the range of N bits of the same number N. For example, T21 of the time axis switching unit output TS is replaced with S21 of the spread spectrum unit output SS. It is located in the chip section at the corresponding time.

In the case where the output TS of the time axis switching unit in the above-described second specific example is used, the same as the first specific example of the replacement of the spread spectrum signal described with reference to FIGS. Then, the time axis reverse permutation unit 11 performs the time axis reverse permutation, then performs the spectrum despreading in the spectrum despreading unit 13, and calculates the average value for a 1-bit section in the average value acquisition unit 15. As for the interference wave component delayed by
Since the information signal converges to a certain constant M, the information signal can be separated and reproduced.

The above-described second embodiment has substantially the same operation and effect as the first embodiment. However, as in the first specific example, there is no operational effect due to the random replacement. Therefore, it is desirable to use a code having a large spread spectrum code (for example, a code having a large order in the case of a PN signal) so as to increase the irregularity in the wireless transmission section so as to obtain sufficient characteristics for spread spectrum. .

Instead, the replacement range of the time axis is always evenly allocated to the N-bit time domain. This means that the time diversity works equally, and the effect of time diversity is expected to be uniform for all symbols of the original transmission information signal I to be transmitted. Further, in this specific example, the time axis can be switched with a simpler algorithm than in the case of the first specific example in which the switching is performed at random. It has the advantage of being easy to do.

In the above description, only the first and second specific examples are shown as the sorting rules, but the present invention is not limited to these. At this time, as a result of the rearrangement, it is desirable that the signals existing in the chip section in the same symbol are uniformly distributed so that they do not converge on the adjacent or near side. In the case of the second specific example, this condition is satisfied. If the transmission quality happens to be reduced during the period of convergence or closeness, the effect of the rearrangement is lost. In addition, as a result of the rearrangement, it is desirable that the signals in the chip section in the same symbol are not periodically distributed. In the case of the first specific example, this condition is satisfied. When this cycle coincides with the cycle of periodic fading, the effect of rearrangement is lost.

In the above description, the carrier is not modulated for the sake of simplicity, but the carrier may be modulated. For example, on the transmitting side, the carrier is modulated by the PSK modulation method or the like with the output TS of the time switching unit in the frequency conversion unit 5 shown in FIG. 1, and on the receiving side, the reception signal is converted in the front end 9 shown in FIG. Demodulate by multiplying by the carrier. Alternatively, it is also possible to modulate the carrier with the transmission information signal I, multiply the output of the spectrum despreading unit SRC with the carrier, and demodulate it. In this case, in the spectrum spreading section 1 and the spectrum despreading section 13, +1,-
It is multiplied by the spread spectrum code C having a value of 1.

In the above description of the spread spectrum transmission system, the CDMA radio transmission system is not particularly premised. However, even in the CDMA radio transmission system having multiple channels, the spread spectrum unit and the despreading unit for each channel are not used. Can be used.

[0056]

As is evident from the above description, the present invention makes it possible to easily remove an interference wave component generated due to the complicated multipath propagation path with a simple configuration. Yes, and a time diversity effect can be provided. Since the configuration is simple, it is easy to make an IC and it is economical. In addition, since a process of checking the state of the propagation path is not particularly required, processing can be performed in a short time, and the response characteristics are excellent. Due to the short processing time,
The present invention can be applied to a portable device that moves at high speed.

As a result, 10 M
Transmission at bps or more can be easily realized, and the means for realizing the transmission can be greatly simplified as compared with the related art. Unlike the conventional adaptive antenna, there is no need for a function to detect an incoming wave or a function to change the directivity. Complex functions such as a delay circuit and a function to weight the output of the delay circuit like RAKE reception Is unnecessary.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmission device used in an embodiment of a CDMA wireless transmission method according to the present invention.

FIG. 2 is a block diagram of a receiving apparatus used in an embodiment of the CDMA wireless transmission method according to the present invention.

FIG. 3 is an explanatory diagram of a first specific example of replacement of spread spectrum signals by the transmission device shown in FIG. 1;

FIG. 4 is an explanatory diagram of a first specific example of the despreading of the received signal corresponding to the first specific example of the replacement of the spread spectrum signal shown in FIG. 3;

FIG. 5 is an explanatory diagram of a second specific example of exchanging a signal spread spectrum in the transmitting apparatus shown in FIG. 1;

FIG. 6 is a schematic configuration diagram of a spreading unit of a conventional CDMA spread spectrum system.

FIG. 7 is a signal waveform diagram for explaining an operation example of the spreading method shown in FIG. 6;

FIG. 8 is a waveform chart for explaining an example of multipath reception.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Spread spectrum part, 2 ... Spread spectrum code memory, 3 ... Time axis replacement part, 4 ... Time axis replacement code memory, 5 ... Frequency conversion part, 6 ... Power amplifier, 7 transmitting antenna, 8 ... Receiving antenna, 9 ... Front end, 10
... A / D converter, 11: time axis reverse permutation unit, 12: time axis reverse permutation code memory, 13 ... spectrum despreading unit, 14 ... spectrum despreading code memory, 15 ... average value acquisition unit, 16 ... identification unit .

Claims (6)

[Claims] An information signal is spectrum-spread by a spreading code, and an arrangement order of the spread signal on a time axis is exchanged according to a predetermined rule with a chip section of the spreading code as a unit, and transmitted. The arrangement order on the axis is exchanged by a rule opposite to the predetermined rule with the chip section as a unit, spectrum is despread with respect to the exchanged signal, and the bits of the information signal are determined based on the despread output. A spread spectrum transmission method characterized in that the information signal is identified for each section. 2. The spread spectrum transmission method according to claim 1, wherein the predetermined rule is to randomly rearrange the sequence of the spread signals on a time axis using random numbers. 3. The predetermined rule is that the spread signal in the n-th chip section of the bit section corresponding to the m-th symbol of the information signal corresponds to Smn, and the spread signal corresponds to the m-th symbol of the information signal. The output after replacement in the n-th chip section of the bit section
2. The spread spectrum transmission method according to claim 1, wherein when mn is set, Tmn is replaced so that Tmn = Snm. 4. The information signal is transmitted in packets, and the range in which the order of arrangement on the time axis is exchanged is the entire range of the duration of the packet of the information signal. The spread spectrum transmission method according to any one of claims 1 to 3. 5. A first means for spectrum-spreading an information signal by a spreading code, and an arrangement order on the time axis of an output of said first means is switched according to a predetermined rule in units of chip sections of said spreading code. A transmitter for spread spectrum transmission, comprising a second means for outputting. 6. A third means for changing the arrangement order of the received signals on the time axis in accordance with a predetermined inverse conversion rule in units of a chip section of the spread code, and outputting the same. , A fourth means for performing spectrum despreading, and fifth means for identifying the information signal for each predetermined bit section of the information signal based on an output of the fourth means. Receiver for spread transmission.