JP3274885B2 - Spread spectrum communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention removes interference waves from each other,
The present invention relates to a spread spectrum communication method capable of efficiently transmitting data.

[0002]

2. Description of the Related Art In a spread spectrum communication method, a carrier wave modulated by data D to be transmitted is spread over a relatively wide frequency band and transmitted, so that transmission power per unit frequency is small and interference with other communication is prevented. There are many features in that they are hardly affected, are hardly affected by external noise, and are excellent in secrecy. As a method of performing spread spectrum communication via a wireless communication path, a method shown in FIG. 17 is generally used. That is, in this communication method, the transmitter T ₁
Is a pseudo noise (hereinafter referred to as P) having the same bit cycle length as the data D to be transmitted by the first multiplier 2.
N-sequence), for example, multiplying and modulating by a M-sequence which is generally widely used therein, and further modulating a carrier having a frequency f ₀ generated by the oscillator 1 by a second multiplier 3. after spread spectrum carrier containing data D by sending to the receiver R ₁ via the wireless communication path.

On the other hand, the receiver R _l is comprises a sequence generator 4 for generating the same M-sequence code and the transmitter 1, the transmitter T ₁
Is transmitted to the amplifier 5 via an antenna (not shown) and amplified to a required level, and then the amplified signal and the local signal f _{L of the} local oscillator 6 are transmitted.
(≒ f ₀ ) is mixed by a mixer 7 and taken out through a low-pass filter to convert the incoming spectrum spread signal into a baseband spread signal. The baseband spread signal is applied to a multiplier 8 where a correlation is obtained between the M sequence of the transmitting side T _{1 and} the M sequence of the sequence generator 4, and the correlation output is converted to the M sequence of 1 by an integrator. The integration for a frame period is performed, and this integrated output signal is detected by a detector 1
At 0, the original information data D is demodulated by detection at the end of the frame. Further, the demodulated data is input to the control terminal of the sequence generator 4 via the synchronization detector 11, and the sequence generator 4 is controlled so that the phases of the M sequences of the transmission side T ₁ and the receiver R ₁ are synchronized with each other. Controls M-sequence generation timing.

However, in the conventional communication method as described above, the M of each of the two communication stations A and B that do not wish to communicate with each other.
Even if the correlation value between the sequences is close to zero, if the two communication stations are located at a short distance from each other, the transmitted wave of each station becomes a high-power interference wave for the other station, so the first-stage amplifier of each receiver R ₁ Saturates to greatly impair the correlation demodulation operation. Conventionally, as a method for solving this problem, as shown in FIG.
And a power control method for controlling the transmission power of each station in accordance with the distance from the base station E. That is, when the stations wish to perform data communication with each other between the communication stations A and B and between the stations C and D, the stations transmit data to each other via the base station E, and transmit power and directivity of each station. Is set in accordance with the distance and the positional relationship between the own station and the base station E, thereby preventing saturation of the first-stage amplifiers of the receivers.

However, in the spread spectrum communication method described above, the directivity of the antenna of each station is inferior and the beam width cannot be reduced, and the distance between each communication station and the base station is smaller than the distance between each communication station and the base station. When they are extremely small, mutual interference cannot always be prevented. For example, referring to the example of FIG. 18, since the distance between the communication stations A and C is significantly smaller than the distance between each of these stations and the base station E, each transmission wave is transmitted from the base station E to the other station. The interference wave becomes much larger than the power of the desired wave, and there is a problem that saturation of the first-stage amplifier of each receiver of the communication station cannot be prevented.

In order to solve such a problem, there has been proposed a means for removing an interference wave having a very large transmission power by using a frequency hopping (FH) system. There is no known method of making a hopping pattern that can be made uncorrelated. To switch the oscillation frequency of the phase control oscillator (PLO) for generating an output signal of the FH system at a high speed, the PLO uses an integrated value of the input. Since it is difficult to increase the hopping speed because it is difficult to operate, there is a problem that it cannot be used as a practical communication method.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional spread spectrum communication method. Even if a receiver receives an interference wave having a very large power, the first stage amplifier can be used. It is an object of the present invention to provide a spread spectrum communication method which is effective in preventing saturation and realizing high-efficiency transmission means for transmitting multi-value information per frame as needed.

[0008]

SUMMARY OF THE INVENTION To solve the above problems , the present invention provides
In a spread spectrum communication method in which each bit value of data to be transmitted is multiplied by a PN sequence code and transmitted, non-inverting and / or non-inverting a PN sequence code unit having a short cycle length so that overlapping of frequency spectra is reduced. A plurality of PN array codes consisting of inverted array patterns are created, and one or more of them are assigned to each communication channel.
According to the sign of each row of the N-row, N-column Hadamard matrix
The PN sequence code units are arranged so as to be non-inverted or inverted.
These are referred to as the PN array codes. Also, on the receiving side
Then, an interference wave is removed using a filter corresponding to the frequency spectrum pattern of each PN array code of the reception channel . In other words, the present invention focuses on the fact that, as a unit, an M sequence having a relatively short cycle is used as a unit, and a spectrum spread by a sequence in which a plurality of M sequences is arranged becomes discrete in a comb shape. By allocating to channels and performing adaptive control, the occupied bands can be shifted so that they do not overlap each other, and each spectral component is separated and suppressed in the frequency domain by an appropriate filter to prevent interference in the high frequency part of the receiver Is what you do. Further, by providing a means for limiting the data to be transmitted to within the frequency band of the data rate, a cross-correlation value between the data and another spreading code provided on the receiving side is made close to zero. Also, PN
By inserting a band limiting filter between the sequence code generator and the multiplier or on the output side of the multiplier, the transmission signal is limited within the range of the main spectral band.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments, an alternate M-sequence and its characteristics will be described in detail in order to facilitate understanding of the present invention. FIG. 1A shows a signal waveform when data to be transmitted is subjected to BPSK modulation.
This shows a case where spreading modulation is performed by appropriately combining a non-inverted sequence M (+) and an inverted sequence M (-) of M sequences corresponding to 1 "and" 0 ", in which case the sequence length is M ₀ ^*. = 2 ^m -1
Consider a relatively short small M sequence (where m is an arbitrary positive integer), arrange N = 2 ⁿ (where n is an arbitrary positive integer) array constants, and set the frame length to MF = NM ₀ ^A spreading sequence represented by ^* is created, and this is made to correspond to the data period T. FIG.
The arrangement pattern P ₀ shown in (b) is obtained by arranging eight M ₀ ^* (+) (indicated as + in the figure). FIG. 1 (c)
The array patterns P _{1 to} P ₃ shown in FIGS.
₀ ^* (+) and M ₀ ^* (-) (shown as-in the figure) are alternately arranged. The series of + and-shown in this column is shown in FIG.
, Ie, 4 rows in an 8 × 8 Hadamard matrix. Here, P _{0 to} P ₃ are referred to as a basic alternation M sequence.

FIG. 3 shows an example of such a spectrum of the alternating M series. If the fundamental wave of each array pattern is f _i ,
Its spectrum consists of an integer multiple harmonic of f _i. The vertical axis in the figure is a voltage value when ± 0.5 V is made to correspond to two values of the spreading sequence. The pattern of i の 0 is the fundamental wave f _i
Has only odd-numbered frequency components.

Here, assuming that the clock frequency is fc and the data transmission rate is fd, the following relationship is given from the configuration of FIG. fc = NM ₀ ^* f _d (1) N = 2 ⁿ (2) M ₀ ^* = 2 ^m −1 (3) From these, the fundamental wave component of each array pattern Pi is P ₀ : f ₀ = Nf _d = C ₀ f _d = f _c / M ₀ ^* (4) P _i : f _i = Nf _d / 2 ⁱ = cif _d = fc / (2 ⁱ M ₀ ^* ) (i ≠ 0 (5) c _i = N / 2 ⁱ (i ≠ 0) (6) Also, when expressing the harmonic component of each array pattern Pi, P ₀ : f _0k = kf ₀ [k = 1, 2, 3,... (M ₀ ^* −1) (7) P _i : f _ik = k ₀ f _i [k ₀ = 1,3,5, ... (2 ⁱ -1) M ₀ ^* ] [i = 1,2,3, ... (N _S -1) )] (8) where, n _S is the number of kinds of patterns of alternating M-sequence, n _S = the _{(log 2 n) + 1 =} n + 1 (9) , including P _0.

Accordingly, the alternation M series corresponds to P in FIG.
_{With the} exception of ₃ , taking into account the band expansion (± f _d ) to both sides of each line spectrum due to multiplication with the data input, and as described above, even if each of the alternating M sequences is created with the same M sequence, The cross-correlation of these spread-modulated waves can be made zero without overlapping the spectrums of the patterns, and if the frequencies of these spread-modulated waves are assigned to each communication channel and separated and extracted, communication can be performed. It is possible to suppress interference waves that affect each other, and it is possible to prevent saturation of the first-stage amplifier as described above.
The present invention eliminates an interference signal according to the above-described principle. Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 4 is a block diagram showing one embodiment of a transmitter and a receiver of a spread spectrum signal for implementing the method according to the present invention. In the figure, T ₂ is a transmitter,
An oscillator 12 for generating a carrier wave of a frequency f ₀ , and a code generator 13 for generating a sequence code as described later, wherein the first multiplier 14 modulates the sequence code with data D to be transmitted, The carrier wave including the data D is spread spectrum by multiplying and modulating the carrier wave with the modulation signal by the multiplier 15 of ₂ and then transmitted to the receiver R2 via the radio communication path.

[0014] On the other hand, the receiver R ₂ is comprises a code generator 17 for generating the same sequence code and the local oscillator 16 and the transmitter T ₂ for generating a local signal of a frequency f _L, as is referred from the transmitter T ₂ Filtered spread spectrum signal
8 and the local signal f _L (≒ f ₀ ) are frequency-mixed by a mixer 20 and passed through an LPF to reduce the incoming spectrum spread signal to a baseband spread signal. Convert to Further, a correlation is obtained between the sequence code and the baseband signal by a multiplier 21, and an output signal obtained by integrating the correlation signal by an integrator is detected by a detector 23 at the final time point of the M-sequence frame. , And demodulates the transmitted information data D.

Here, as shown in FIG. 5, a transmitter T ₂ and a receiver R ₂ are provided for each of the communication stations A, B, C and D, and between the communication stations A and B and between the communication stations C and D. Considering the case where data communication is performed with each other, communication stations A located close to each other
C and C will be described below to prevent the transmission waves from interfering with the other receiver.

First, the communication stations A and B communicate with each other as shown in FIG.
Pattern of first row of next Hadamard matrix "++++++++
The sequence M _A ⁺ obtained by non-inverting the M sequence M _A having a sequence length of M ₀ ^* = 2 ^m -1 [bit] according to each symbol of “+” as shown in FIG. The number of frames arranged is M
_F = 8M ₀ ^* sequence code P _A code generator 13 of the bit]
And 17 are generated according to each bit value of the data D. The filters 18 of the communication stations A and B respectively
Frequency f _c1 = 8f _d k as shown in (a) (where, k =
1,2,3, ..., at the center frequency of M ₀ ^* -1), spectral bandwidth using what can be extracted frequency components of f _d, by diffusing carrier including data D in sequence code P _A The spread signal is used as a communication medium between the two stations.

On the other hand, the communication stations C and D communicate with each other as shown in FIG.
Pattern of second row of next Hadamard matrix "+-++-++
- depending on each symbol of ", the M-sequence M _A was allowed to noninverting sequence M _A ⁺ sequence obtained by inverting the M _A ^- and the aligned the array constant N = 8 or alternately as shown in FIG. 7 And the frame length is M _F =
8M ₀ ^* [bit] sequence code P _B is generated from code generators 13 and 17 in accordance with each bit value of data D.
Also, the communication station C and the frequency as the filter 18 shown in FIG. 3 (b) of the _{D f c2 = 8f d / 2k} 0 ( where, k ₀
= 1, 3, 5,..., M ₀ ^* ) and the bandwidth is f
_The one that can extract the frequency component of _d is used, and the sequence code P
_A spread spectrum signal obtained by spreading a carrier wave including data D at _B is used as a communication medium between both stations.

In this way, the communication stations A and B transmit the spectrum of the spread spectrum signal, which is multiplied and modulated by the respective transmitters with the sequence code P _A , as shown in FIG.
c ₁ and its integral multiple harmonic components, the width of each spectrum becomes f _d , and each spread spectrum signal is input to the first-stage amplifier through the filter 16 of the partner station. Communication can be performed without receiving interference from the station. Similarly, in the communication stations C and D, the spectrums of the spread spectrum signals multiplied and modulated by the respective transmitters with the sequence code P _B have the frequency fc _{2 as} shown in FIG.
And it becomes an odd multiple harmonic components, since the width of each spectrum becomes f _d, a spread spectrum signal of each is demodulated through the filter 18 of the other station, both stations without being mutually channel interference Can communicate. Furthermore,
The spectrums of the spread spectrum signals transmitted by the communication stations A and C do not overlap each other as shown in FIGS. 3A and 3B, and the transmission waves of both stations are respectively filtered by the filter 1 of the other station.
8, the saturation of the first-stage amplifier of each receiver can be prevented, and both stations can perform the intended communication so as not to hinder each other's demodulation operation by the respective transmission waves.

In this embodiment, the means for solving the problem when the first-stage amplifiers of the two communication stations are saturated has been described.
The present invention is not limited to this. By changing constants such as the array constant N when generating each pattern of the above-described alternating M series, it is possible to create a large number of patterns whose spectra do not overlap. By allocating a sequence code based on a pattern to each communication station, mutual interference can be similarly suppressed between a plurality of communication stations.
Further, the alternation M sequence is not limited to the above-described one, and as shown in FIG.
Alternatively, a sequence in which inverted sequences are arranged in accordance with the sign of the M sequence may be assigned to a predetermined communication station, and the above-described effect can be obtained.

In the above-described embodiment, the alternation M sequence is assigned to a predetermined communication station. However, the present invention is not limited to this, and various modifications can be made as follows. FIG. 9 (a) is a diagram showing a configuration example of another sequence code. Considering a first-order small M-sequence M ₁ ^* , its constituent elements are assumed to be a zero-order small M-sequence M ₀ ^* , and an M-sequence M ₁ ^* Are arrayed in N array constants, and each element of the M series M ₁ ^* is non-inverted and inverted according to + and − of the array pattern in the N-order Hadamard matrix. That is, as shown in FIG.
₁ ^* according to each bit value of, for example, series M ₀ obtained by inverting the M-sequence M ₀ ^* In the case of the bit value of the sequence is '1'
^{* +} , And when the bit value is '0', the M sequence M ₀ ^*
Is series M ₀ ^* was inverting the ^- a generates the M-sequence M ₁ ^* sequence length min aligned series in M _B, for each pattern of each row of the array constant N = 2 ⁿ order and the Hadamard matrix, the sequence M
_The sequence codes P _B1 , P _B2 , P _B3 ,... _Are arranged such that a sequence M _B ^{+ obtained by} inverting _B and a sequence M _B ⁻ obtained by inverting _B are arranged in an array constant N = 2 ⁿ .
Is configured. This sequence will be referred to as a re-spread type P (MMN) from the sequence combination mode. This means is effective in forming a large number of streams.

FIG. 10 (a) shows an example in which the combination order of the P (MMN) sequence is transposed, and is also referred to as a re-spreading P (MNM) sequence. That is, this P (MN
M) The sequence has an array constant N = 2 ^{n as} shown in FIG.
A sequence M obtained by inverting the 0th-order M sequence M ₀ ^* according to each pattern for each pattern of each row of the Hadamard matrix whose order is
₀ ^{* +} and sequence is obtained by inverting M ₀ ^{* -} the array constant N pieces side-by-side series _{M c1, M c2, M c3} , ... to generate a, it, etc. series _{M c1, M c2, M c3} , ... each the primary M-sequence M ₁ ^* according to each bit value of the non-inverted so the sequence and 1 inverted so the sequence order M sequence M ₁ ^* sequence length fraction arranged as series code P _c1,
P _c2, P _c3, which was composed of ..., this technique is also effective in constructing a large number of sequences.

Note that a part of the spectrum of the re-spread type P (MMN) and P (MNM) sequences corresponding to the arrangement patterns P ₁ and P ₂ is M ₀ ^* = M ₁ ^* = 7 and N = 8. The cases are shown in FIGS. 11A to 11D, respectively. P (MM
The N) sequence shows essentially the same aspect as the basic alternation M sequence described above, and the expressions (4) to (8) hold (however, the expressions (4) to
Certain M ₀ ^* must be replaced by M ₀ ^* M ₁ ^* in (8)). On the other hand, the P (MNM) sequence is centered on the line spectrum of the basic alternating M sequence, and the line spectrum of the sideband of the primary M sequence M ₁ ^* is arranged over the range of ± M ₁ ^* f _d around the P (MNM) sequence. For example, for P ₁ (MNM), M ₀ ^* Nf _d / 2 =
28f _d and its k ₀ times around, a line spectrum spread over a range of ± 7f _d. The re-spreading sequence shown here is a P (MMN) sequence and a P (MNM) sequence as described above.
Not limited to the sequence, each row of the M-sequence or N-order Hadamard matrix is used as a basis, and the non-inverted and / or inverted sequence is repeatedly arranged according to the sign of each row of another M-sequence or N-order Hadamard matrix. It is good if it is a series.

[0023] Although considered those in each of the above-described embodiments by arranging an array constant N = 2 ⁿ pieces of M-sequence as a sequence code used at each communication station, the present invention is to arrange not limited to this M
When α ₁ , α ₂ , α ₃ ,... Α _p are each an arbitrary prime number, the number N of sequences is expressed by the following equation: N = 2 ⁿ · α ₁ · α ₂ · α ₃ ···
It may be a number calculated by the product of at least one prime number and a power of 2 as represented by α _p (10). In this case, the following equation the formula (10) in order to M ₀ ^* alternating pattern in one frame is _{completed, c i = N / u i} (i = 0,1,2, ...) (11 ) (Where c _i represents the number of cycles / frame and u _i represents the number of units / cycle of M ₀ ^* ), and the value of equation (10) that satisfies this is selected.

In this example, the pattern for non-inverting or inverting each of the M sequences forming the sequence code is, for example, the above-mentioned N is a product of 2 ³ and a prime number 3, that is, N = 24. In the case where the inversion is represented by symbols + and-, respectively, if an alternating pattern of + and-is determined as an array satisfying the above conditions as shown in FIG. 12A, the pattern becomes one frame length of the sequence code. It can be completed at
The sequence code generated in this manner is called a common multiple form from that aspect, and the spectrum of each sequence code should not overlap each other based on the pattern of non-inversion and inversion of the M sequence similarly to the above-described sequence code. Can be. FIG.
(B) represents the line spectrum of each pattern in this example. In this case, unlike in the case of N = 2 ⁿ , the frequency components slightly overlap between the arrangement patterns, but the overlapping point is represented by the following equation c _i k ₀ = c _j k ₀ ′ (k ₀ , k ₀ ′: odd number)
Since (12) is satisfied and the number of overlapping points is very small, the array pattern in this example has an array constant N =
2 ⁿ no practical problem even when compared to that of, and the type N _S of the arrangement pattern c _i c _i = 1 Tosureba the case where is positive equation _{N S = Σc i [c i} = Positive number] (13).

Also, in the alternating M series and the re-spreading series described above, the spectra may partially overlap. However, if the overlapping degree is small, the effect of the present invention can be similarly obtained without practical problems. Can be In other words, the effect of the present invention is great when a sequence code whose frequency spectrum does not overlap each other, that is, a sequence code whose correlation value in the frequency spectrum is mutually zero is assigned to each communication station, but the present invention is not limited to this. However, if the correlation value in the mutual frequency spectrum is small, it is sufficient to prevent the saturation of the first-stage amplifier.

Furthermore, the alternating M-sequence described above in the case of using only the arrangement pattern of FIG. 2, the total address volume N _A total address volume N _A ^* and BPSK method when considered to utilize this kind of pattern in the address space If a is H (M ₀ ^*) as a function of M-sequence length determining the number of available sequences in the case of M ₀ ^* equation ^{_{N a * = N S · H}} (M 0 *) (14) N a
= H (NM ₀ ^* ) (15) Here, the value of H (NM ₀ ^* ) is generally NM ₀ ^* ≠ 2 ^m −1, and two neighboring M sequences, M _E1
And M _E2 are selected, and the proportional distribution value of H (M _E1 ) and H (M _E2 ) is set as an approximate value.

From these two equations, the address efficiency η is defined as the following equation η = N _A ^* / N _A (16), and log ₂ (N _B : number of bits / frame) is taken on the horizontal axis. As a result of the simulation, the address efficiency η of the alternating M series is represented as a solid line in FIG. As is clear from this figure, if a relatively small value is used as N for the alternating M sequence, η> 1 and BPSK
This is advantageous from the viewpoint of increasing the number of arrangement patterns.
From a practical point of view, it can be understood that when N is increased to increase the number of array patterns, the address efficiency periodically increases and decreases, and the maximum address efficiency appears cyclically in each case.

Similarly, FIG. 13 shows other sequences, that is, the common multiple type sequence, the re-spread type P (MMN) sequence, and the P (M
The results of the simulation of the address efficiency η for the NM) series are shown by the dotted line, the one-dot chain line, and the two-dot chain line, respectively, each having unique characteristics, and the efficiency maximum value tends to appear periodically as N increases. This is similar to the above basic alternation M series.

In the above-described embodiment, sequence codes whose frequency spectra do not overlap each other are assigned to each communication station in advance. However, the present invention is not limited to this, and the first-stage amplifier is affected by transmission waves of other communication stations. When a problem occurs, the frequency spectrum of the transmitted wave is analyzed, and the sequence code required to generate a transmitted wave having a spectrum that does not overlap the frequency spectrum is changed. Is changed so that only the changed spectral components can pass. In order to change the sequence code during communication, it is necessary to notify the partner station of the change. For this purpose, a method of transmitting low-speed control information using an extremely long M sequence, an FH method, or the like is used. Utilization of is considered.

Alternatively, the present invention relates to a system in which a plurality of communication stations communicate with each other via a base station as described above.
If the first-stage amplifier is disadvantageous due to the influence of the transmission wave of another communication station, as described above, a required number of sequence codes having a small correlation value in the frequency spectrum are allocated to each of the communication stations, and It is obvious that a station can be applied if a filter capable of passing only the spectrum of the sequence code assigned to the station is provided before the first-stage amplifier. In the above-described embodiment, the means for solving the problem of the saturation of the first-stage amplifier with the sequence code having a small overlap between the frequency spectra has been described. However, the present invention achieves not only such an object but also the following object. be able to.

That is, the M-sequence code and the data to be transmitted as described above are generally constituted by rectangular waves. For this reason, a large number of unnecessary signal components are generated in the spread spectrum signal due to the harmonic component of the rectangular wave, and the frequency of the unnecessary signal component and the frequency of the original spread spectrum signal component are very close to each other or are mixed. Therefore, it is very difficult to distinguish between the two. Therefore, it is practically impossible to make the correlation value between a plurality of spread spectrum signals zero.

In order to solve this problem, in the present invention, FIG.
As shown in FIG. 4, a filter capable of passing only the frequency component based on the above-mentioned sequence code on the transmission side is provided at the subsequent stage of the spread spectrum multiplier. In this way, the unnecessary signal components as described above can be removed by the filter, so that the correlation value between a plurality of spread spectrum signals can be made close to zero, and S / S
This is effective in improving N.

To obtain the same effect, the filter is provided before the spread spectrum multiplier, or a filter for removing a harmonic component of the data to be transmitted, that is, the data is placed in the frequency band of the data rate. It is obvious that a filter for limiting may be provided, and the filters described here may be appropriately combined. Further, the means for obtaining the effect shown here is not limited to this. For example, as shown in FIG. 15, a spectrum spread signal from which the unnecessary signal component is removed is stored in a memory, and a data value to be transmitted and a PN array code are transmitted. A predetermined address of the memory may be determined from a type by a logic circuit, and a required spread spectrum signal may be read from the memory.

Further, in the above-described embodiment, a sequence code having a small overlap of the frequency spectrum is allocated to each communication channel to solve the problem of the saturation of the first-stage amplifier, but the transmission is performed using all the Hadamard matrix patterns shown in FIG. Can be realized. This is because the patterns in FIG. 2 are orthogonal to each other. For example, when transmitting from the station A to the base station E, one of the patterns in a plurality of types M ₀ ^* is changed to (A →
E) Predetermined for communication, station A selects any one of the eight patterns of FIG. 2 based on two M ₀ ^* (M
₀ ^* N bits). The station E prepares a total of 16 demodulators for discriminating inversion and non-inversion of eight patterns, and identifies a correlation pattern of a demodulator that has transmitted any one of the maximum correlation outputs as a transmission pattern. I do. In this case, a code sequence of one frame (M ₀ ^* N bits)
Is transmitted, log ₂ (N × 2) [when N = 8, log ₂ (8 × 2) = 4] bits / frame can be transmitted. That is, multilevel transmission can be realized by selecting a pattern of the Hadamard matrix. The address efficiency in this case is equivalent to doubling the vertical axis of FIG. 13, and therefore η is almost always greater than 1. That is, it is more advantageous than the case where a normal simple M sequence is used. In the above case, there is no effect of solving the saturation problem. However, FIG.
For example, for three paths, the following transmission paths (A → E): P ₀ , P ₁ (2 bits / frame) 〃 (B → E): P ₂ , P ₄ (2 bits / frame) 〃 (C → E): When patterns are assigned such as P ₃ , P ₅ , P ₆ , P ₇ (3 bits / frame), the path is 2 per frame.
Up to 3 bits can be transmitted. Moreover, even if signals for different paths enter as interference, the cross-correlation between code sequences belonging to different paths can be close to zero (although there is a little between and with the code sequence of the path). Also, the patterns in the same path have the same spectrum, but are orthogonal to each other, so that as long as synchronization is ensured (a condition normally satisfied in transmission on one path), mutual interference becomes zero. Therefore, it is possible to realize multi-level transmission while dealing with the near-far problem. The address efficiency in this case has a high value as in the case where all the Hadamard patterns are exclusively used by one route.

As described in the above embodiment, a plurality of bits of binary data to be transmitted can be used for the multi-level data transmission means in association with the sequence code. Possible communication volume can be increased. Also, the number of patterns of the PN array code used here is N
, The effective band reduction rate β is given by the following equation: β = (log
Represented by ₂ 2N) ^-1 (17), since the pattern number N can be increased as described above, the reduction rate β may be reduced, in order to effectively utilize the frequency band of the communication channel, convenient Would be good.

Furthermore, the present invention can be used as a frequency diversity communication system by transmitting the same data using a plurality of sequence codes that do not overlap in frequency, and is effective in improving fading resistance. Will.
Further, as described above, the present invention provides a plurality of PNs having a small correlation value.
When transmitting the same data multiple times using an array code,
An RC code is added to the data, and the C
If only a good received signal is demodulated from the result of the RC code, it will be convenient in improving the communication error rate.

In the above embodiment, the present invention is used for wireless communication. However, it is obvious that the present invention is not limited to this and can be used for wired communication. Also, as shown in FIG. 16, in the conventional means in which a plurality of communication stations perform spread spectrum communication with each other via a wired communication path, the receiver of each communication station uses transmission characteristics that are deteriorated due to the transmission characteristics of the wired communication path. In some cases, the S / N is improved by using an equalizer for the signal. However, when a transmission signal attenuated in a predetermined frequency region is amplified by an equalizer,
Since noise is also amplified, there is a limit to the improvement of S / N. On the other hand, the present invention can concentrate the frequency pattern of the spread spectrum signal on a predetermined frequency as described above, so that a spread spectrum signal having a frequency pattern that avoids a frequency region having poor transmission characteristics is used. By setting a sequence code, each communication station can separate a signal component desired to be demodulated from an unnecessary noise component, and can suppress only many noise components with a filter. It will be effective in improving S / N.

Further, in the above embodiment, the transmitter side modulates the data to be transmitted after spread spectrum, while the receiver side demodulates the signal by mixing the spread spectrum signal with the carrier frequency signal, and then despreads. However, even if the order is changed, only the characteristics of the filters to be arranged thereafter are different, and there is no fundamental difference.

[0039]

As described above, according to the present invention, a required number of sequence codes having a small correlation value in the frequency spectrum are allocated to communication stations not wishing to communicate with each other, and the first stage of each of these communication stations is allocated. A filter that can pass only the spectrum of the sequence code assigned to its own station is provided at the front stage of the amplifier to suppress a high-power spread-spectrum signal transmitted from a station that does not desire communication. This is effective in providing a spread spectrum communication method capable of preventing saturation of the first-stage amplifier due to a signal and performing smooth communication.

[Brief description of the drawings]

FIGS. 1A to 1E are diagrams for explaining an alternating M-sequence according to the present invention.

FIG. 2 is a diagram showing an array pattern of an eighth-order Hadamard matrix.

FIGS. 3A to 3D are characteristic diagrams showing a spectrum of an alternating M series.

FIG. 4 is a configuration diagram showing one embodiment of the present invention.

FIG. 5 is a diagram for explaining one embodiment of the present invention.

Shows the sequence code P _A to be used in an embodiment of the present invention; FIG.

FIG. 7 is a diagram showing a sequence code P _B used in one embodiment of the present invention.

FIG. 8 is a diagram for explaining another alternating M-sequence according to the present invention.

9A and 9B are diagrams showing a configuration example of another sequence code (respread P (MMN) sequence) according to the present invention.

FIGS. 10A and 10B are diagrams illustrating a configuration example of another sequence code (respread P (MNM) sequence) according to the present invention.

FIGS. 11A to 11D are characteristic diagrams showing spectra of a re-spread type P (MMN) sequence and a P (MNM) sequence.

12A and 12B are a diagram showing a configuration example of another sequence code (common multiple type sequence) according to the present invention and a diagram showing its spectrum.

FIG. 13 shows the address efficiency η of each of the sequence codes according to the present invention.
FIG.

FIG. 14 is a configuration diagram showing another embodiment of the present invention.

FIG. 15 is a configuration diagram showing another embodiment of the present invention.

FIG. 16 is a configuration diagram showing another embodiment of the present invention.

FIG. 17 is a configuration diagram of a transmitter and a receiver in a conventional spread spectrum communication method.

FIG. 18 is a diagram for explaining a conventional spread spectrum communication method.

[Explanation of symbols]

T ₂ transmitters, R2 receiver, 12 an oscillator, 13 and 17 code generators, 14, 15 and 21 multipliers,
16 local oscillators, 18 filters, 19 amplifiers,
20 mixer, 22 bandpass filter, 23
Detector.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Toshikatsu Naito 2-1-1 Kotani, Samukawa-cho, Koza-gun, Kanagawa Prefecture Toyo Communication Equipment Co., Ltd. (56) References JP-A-64-30340 (JP, A) JP-A-62-45232 (JP, A) JP-A-4-150332 (JP, A) JP-A-2-143740 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1 / 69-1/713 H04J 13/00-13/06

Claims (4)

(57) [Claims] 1. The data to be transmitted is defined as a period length of the data.
In a spread spectrum communication method in which pseudo noise (PN sequence) having the same bit cycle length is multiplied and transmitted, the above-mentioned video signal is transmitted so that frequency spectrum overlaps are reduced.
Pseudo-noise (PN system)
Column) is converted to an N-by-N Hadamard matrix
Inverting and / or inverted in accordance with the pattern of each line
Plurality create a PN sequence code in which a plurality sequences, the PN sequence
A spread spectrum communication method, wherein one or more types of codes are assigned to respective communication channels. 2. The receiving side allocates the communication channel .
2. The spread spectrum communication method according to claim 1, wherein an interference wave is removed by using a filter corresponding to a frequency spectrum pattern of each of said assigned PN sequence codes. 3. A method for limiting the data to be transmitted within a frequency band of the data rate so that a cross-correlation value between the spreading code and another spreading code provided on the receiving side is close to zero. 3. The spread spectrum communication method according to claim 1, wherein: 4. A code generator for generating the PN array code.
And the data to be transmitted is generated from the code generator.
4. A transmission signal is limited within a range of a main spectrum band by inserting a band-limiting filter between the multiplier and a multiplier that multiplies the PN array code or by inserting a band-limiting filter at an output side of the multiplier. The spread spectrum communication method according to any one of the above.