JP2002076984A - Spread spectrum communication device and majority logic spread spectrum multiplex communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spread spectrum communication device and a majority logic spread spectrum multiplex communication method capable of realizing spread encoding that prevents channels from interfering with each other in major logic spread spectrum multiplex communication. SOLUTION: A first modified Hadamard matrix Ik (k = positive integer) which is obtained by eliminating the first row, or a second modified Hadamard matrix Jk (k = position integer) which is obtained by eliminating the first column of the Hadamard matrix Hk, is used as a spread code PNi in place of an Hadamard matrix Hk which is a kind of an orthogonal code and used as a spread code PNi, so as to prevent channels from interfering with each other in major logic spread spectrum multiplex communication.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication technique for transmitting a signal by spreading the frequency band of the signal over a wide frequency band of several tens of times, and more particularly to an inter-channel communication in spread spectrum multiplex communication using majority logic. The present invention relates to a spread spectrum communication apparatus and a majority logic spread spectrum multiplex communication method capable of realizing spread coding with zero interference.

[0002]

2. Description of the Related Art In general, a spread spectrum communication system is a system for transmitting a signal having a much wider bandwidth than information data. To realize this, there are roughly two systems.

[0003] The first is direct S (Direct S).
equipment (DS) method. In this method, a digitized baseband signal is multiplied by a spreading code such as a high-speed pseudo-noise code to generate a baseband signal having an extremely wide bandwidth compared to the original data, and further to phase shift keying (PSK). : Phase Sh
if Keying, frequency shift keying (FSK:
Modulation such as Frequency Shift Keying is performed, converted into an RF (radio frequency) signal, and transmitted. On the other hand, the receiving side demodulates the original data by performing despreading for obtaining a correlation with the received signal using the same spreading code as that of the transmitting side.

The second is frequency hopping (Freq
This is a method referred to as “energy hopping (FH) method”. In this method, the frequency of a carrier wave modulated by a baseband signal is switched and transmitted at a time interval of one bit of data or an integral multiple thereof or an integral multiple thereof according to a spreading code. The receiving side performs despreading and demodulates the original data by performing a correlation operation of tuning the carrier on the receiver side to the transmitting side using the same spreading code as the transmitting side.

[0005] In these systems (first prior art), by selecting a spreading code from a set having a small mutual cyclic correlation, a system using other spreading codes is not largely affected. In addition, since there is no significant influence from a system using another spreading code, code division multiple access for simultaneous communication in the same frequency band becomes possible.

However, in the first prior art, D
In the case of the S system, the peak of the periodic cross-correlation cannot be set to 0 because a binary code is usually used as the spreading code. In the case of the FH system, the spreading code is multi-valued,
In the case of asynchronous operation which is a general usage, code 1
The same digit collision (hit) can occur during a cycle. Therefore, since such a slight cross-correlation cannot be eliminated, the number of lines that can be simultaneously communicated when performing multiple access is reduced, and compared to other multiple access systems such as frequency division multiple access and time division multiple access. However, there is a problem that the frequency use efficiency is reduced.

[0007] As a prior art for solving such a problem, for example, Japanese Patent Laid-Open No. Hei 6-12093 is known.
No. 1 (second conventional technique). The second prior art aims at avoiding a decrease in the number of multiple access based on the correlation between spreading codes, and according to information of a code selection signal input prior to the start of communication, +
A row or column vector of a Hadamard matrix having 1 and -1 as elements is extracted, and +1 which is an element of this row or column vector is converted to 0 or 1, and -1 is converted to 1 or 0 to form a binary code sequence. Multi-frequency oscillating means for modulating each of the carriers having different frequencies and the same intensity by each bit of the binary code sequence and further modulating all the carriers with this input data for each bit of input data. It is a spread spectrum communication device having the same.

[0008] Now, the spread code (hereinafter, PN _i (i =
1,..., N: i and N are positive integers). A Hadamard matrix, which is a kind of orthogonal code, is used as H _k (k = Positive integer), the relationship of Equation 1 generally holds between the Hadamard matrix H _{k + 1} and the Hadamard matrix H _k .

[0009]

(Equation 1)

[0010] When a high-order matrix is successively obtained, Equation 2 and Equation 2 are obtained.
Higher order Hadamard matrix H such as _kCan ask for
Wear.

[0011]

(Equation 2)

[0012]

(Equation 3)

Specifically, the Hadamard matrix H shown in equation 2
The row vector 13 in ₁ is [11], [1-1].
Becomes The row vector 13 in the Hadamard matrix _{H 2} shown in Equation 3, [1 1 1 1], [1 -1
[1-1-1], [11-1-1], [1-1-1]
11].

According to the spread spectrum communication apparatus of the second prior art, the spread code is developed on the frequency axis, and an equidistant code derived from a Hadamard matrix is used as the spread code, so that the spread code is based on the cross-correlation of the spread code. There is disclosed an effect that a reduction in the maximum number of simultaneous communications at the time of code division multiple access can be avoided.

[0015]

FIG. 4 is a functional block diagram for explaining a main part of a spread spectrum communication apparatus 30 according to a second prior art. In FIG. 4, 27 is a ternary multiplexed signal, PN _i (i = 1,..., N: i, N is a positive integer) is a spreading code, and SG _i (i = 1,..., N: i, N is positive). Is an information code, 30 is a second conventional spread spectrum communication apparatus, 36 is a majority logic decision unit, 38 is a transmission unit,
Reference numeral 39 denotes a receiving unit.

Referring to FIG. 4, the spreading code PN _i of the M-sequence code and the like which are used in the second prior art, it is widely used in mainly due to the ease of the product. However, the second conventional technique has a problem that it is difficult to avoid degradation of noise resistance as a result of inter-channel interference occurring at the time of multiplexing, mainly due to correlation characteristics between spreading codes PN _i . Problem 1).

FIG. 5 is a state diagram of a multiplexed signal before majority logic decision in the second prior art spread spectrum communication apparatus 30, and FIG. 6 is a second prior art spread spectrum communication apparatus 3.
FIG. 6 is a state diagram of a multiplexed signal after majority logic determination at 0. In FIG. 5, F _i (i = 1,..., N: i, N is a positive integer) indicates a multiplexed signal. In FIG. 6, reference numeral 27 denotes a ternary multiplex signal.

As described above, in the second prior art, a Hadamard matrix H _k, which is a kind of orthogonal code, is used for the spreading code PN _i in order to eliminate inter-channel interference during multiplexing. However, since the orthogonal codes such as the Hadamard matrix H _k are square matrices as shown in Expressions 1 to 3, each generated row vector 13 (Equation 5, Expression 6)
If you assign a reference) as the spreading code PN _i, since always an even multiple, the problem that the multilevel in some cases a logical value = becomes "0" in the multiplex signal F _i at the time of multiplexing (the 2 problems). Further, when the majority logic (ML) determination as shown in FIG. 5 is subsequently performed using the majority logic determination unit 36, the majority logic (ML) determination is performed using the logical value = “0” as a threshold value. Therefore, the logical value = “0” cannot be determined, and as a result, as shown in FIG. 6, the multiplexed signal _Fi is a ternary multiplexed signal with logical values = “− 1”, “0”, “1”. 27
(That is, a multiplexed signal F _{i of} logical values = “− 1”, “0”, “1”), which complicates the transmission unit 38 and the reception unit 39 (third problem). )was there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a spread spectrum communication apparatus and a majority logic spectrum which can realize spread coding with zero inter-channel interference in majority logic spread spectrum multiplex communication. An object of the present invention is to obtain a spread multiplex communication method.

[0020]

According to a first aspect of the present invention, there is provided a spread spectrum communication apparatus, comprising: a transmitting section and a receiving section for performing a majority logic spread spectrum multiplex communication; and the majority logic spread spectrum multiplex communication. A means for generating and outputting a first modified Hadamard matrix excluding the first row of the Hadamard matrix, a means for generating and outputting a spread code using the first modified Hadamard matrix, Has a majority logic decision unit for executing a majority logic decision and generating and outputting a binary multiplexed signal represented by two types of logic values. According to a second aspect of the present invention, there is provided a spread spectrum communication apparatus comprising: a transmission unit and a reception unit for performing majority logic spread spectrum multiplex communication; and a first column of a Hadamard matrix during the majority logic spread spectrum multiplex communication. Means for generating and outputting a second modified Hadamard matrix excluding eyes, means for generating and outputting a spreading code using the second modified Hadamard matrix, and executing majority logic decision based on the spreading code. It has a majority logic decision unit that generates and outputs a binary multiplexed signal represented by two types of logical values. Further, claim 3 of the present invention
In the spread spectrum communication apparatus according to the invention described in claim 1, in the invention according to claim 1 or 2, the logical value of the binary multiplexed signal generated and output by the majority logic decision unit is two values of -1 and 1. is there. The majority logic spread spectrum multiplex communication method according to the invention according to claim 4 of the present invention includes a step of executing the majority logic spread spectrum multiplex communication using a transmitting unit and a receiving unit; Generating and outputting a first modified Hadamard matrix excluding the first row of the Hadamard matrix; and generating and outputting a spreading code using the first modified Hadamard matrix.
And a majority logic decision step of executing majority logic decision based on the spreading code and generating and outputting a binary multiplexed signal represented by two types of logic values of -1 and 1. is there. A majority logic spread spectrum multiplex communication method according to the invention according to claim 5 of the present invention comprises the steps of: executing majority logic spread spectrum multiplex communication using a transmitting unit and a receiving unit; Generating and outputting a second modified Hadamard matrix excluding the first column of the Hadamard matrix; and generating and outputting a spreading code using the second modified Hadamard matrix.
And a majority logic decision step for executing majority logic decision based on the spreading code and generating and outputting a binary multiplexed signal represented by two types of logic values of -1 and 1. is there.

[0021] Thereby, majority logic spread spectrum multiplexing communication with zero inter-channel interference can be realized, and the transmission unit and the reception unit can be constituted by digital devices, and are used as the mainstream of the in-vehicle multiplex communication system in trains and automobiles. Time Division Multiplex (Time Division Multiplex)
It is possible to provide a spread spectrum communication apparatus and a majority logic spread spectrum multiplexing communication method capable of improving the compatibility with an Ipe Access (TDMA) system.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below in detail with reference to the drawings. First, a majority logic spread spectrum multiplexing communication method according to the present embodiment will be described.

As mentioned above, the majority logic spectrum expansion
In order to eliminate inter-channel interference during distributed multiplex communication,
Hadamard line, a kind of alternating code
Row H _k(K = positive integer) with the spreading code PN_i(I = 1,
..., N: i, N are positive integers)
Matrix H_kSince orthogonal codes such as are square matrices,
Each row vector 13 to be processed is directly used as a spreading code PN._i(I
= 1, ..., N: i, N is a positive integer)
In addition, since even numbers are always multiplexed, the majority decision logic spectrum expansion
Multiplexed signal F during dispersive multiplexing_i(I = 1,..., N: i, N
Is a positive integer), the logical value = "0"
(See FIG. 4, Equations 1 to 3).

On the other hand, the inventors have found that in order to be sure odd multiple by avoiding the even multiple in performing multiplexed using orthogonal codes, such as Hadamard matrix H _k is the Hadamard matrix H _k It has been found that the first column (that is, the row vector 13 of the first column) should all be 1 or -1.

[0025] For example, in the Hadamard matrix of _{H 2} when the 2 values of k, as shown in Equation 4, the first column (the first column of the row vector 13) [1 1 1 1] and I just need to be.

[0026]

(Equation 4)

However, in general, all
Is a spreading code PN in which _iSpread modulation using
Is the spreading code PN because the signal bandwidth is not spread_iage
Has no meaning.

In the present embodiment, instead of using the Hadamard matrix H _k , which is a kind of orthogonal code, as the spreading code PN _i in order to reduce the inter-channel interference during majority logic spread spectrum multiplexing communication, It is characterized in that a first modified Hadamard matrix I _k (k = positive integer) excluding the first row of the Hadamard matrix H _k is used as a spreading code PN _i .

Specifically, when the value of k is 2, the first
Modified Hadamard matrix I ₂ of the matrix as shown in Equation 5.

[0030]

(Equation 5)

[0031] Thus, by assigning a first modified Hadamard matrix I _k, excluding the first row of the Hadamard matrix H _k in the spreading code PN _i, each column vector 11
Although no longer the orthogonality of (Formula 4 Formula reference 6), since the orthogonality of the row vector 13 can hold, without fail to avoid an even multiple in performing multiplexed using orthogonal codes, such as Hadamard matrix H _k Odd multiplexing can be performed. As a result, there is an effect that the inter-channel interference at the time of majority logic spread spectrum multiplex communication can be reduced to zero. Such a majority logic spread spectrum multiplexing communication method can improve the consistency with the TDMA method used as the mainstream of the in-vehicle multiplex communication method in trains and automobiles.

FIG. 1 is a functional block diagram for explaining a main part of a spread spectrum communication apparatus 10 according to one embodiment of the present invention. 1, reference numeral 10 denotes a spread spectrum communication apparatus according to the present embodiment, 16 denotes a majority logic decision unit,
18 is a transmitting unit, 19 is a receiving unit, 23 is a binary multiplexed signal, P
N _i indicates a spreading code, and SG _i indicates an information code.

Referring to FIG. 1, a spread spectrum communication apparatus 10 according to the present embodiment has a transmitting section 18 and a receiving section 19.
And a spreading code PN _i such as an M-sequence code.
Is used, the first modified Hadamard matrix I _k excluding the first row of the Hadamard matrix H _k is used as the spreading code PN _i .

[0034] Figure 2 is a state diagram of the multiplex signal F _i before majority logic decision on the majority rule spread spectrum multiplex communication method according to an embodiment of the present invention, and FIG. 3 according to an embodiment of the present invention is a state diagram of the multiplex signal F _i after majority logic decision on the majority rule spread spectrum multiplex communication method. In FIG. 2, F _i represents the multiplexed signal. In FIG. 3, reference numeral 23 denotes a binary multiplexed signal.

As described above, in the spread spectrum communication apparatus 10, in order to reduce the inter-channel interference at the time of majority logic spread spectrum multiplex communication to zero, the orthogonal code 1 is used.
Instead of using the seed Hadamard matrix H _k for the spreading code PN _i , a first modified Hadamard matrix I _{k obtained} by removing the first row of the Hadamard matrix H _k is used.
_k is used as the spreading code PN _i .

For this reason, the first modified Hadamard matrix I _k
Since not a square matrix as shown in Equation 5, when assigned a row vector 13 generated as the spreading code PN _i, always possible to realize an odd multiple. That can eliminate the cases where multilevel multiple signal F _i at the time of the majority logic spread spectrum multiplex communication becomes logical value = "0".
After the assignment, the majority logic (Majority L) as shown in FIGS.
logic: ML) When the judgment is performed, the logical value =
Since the majority logic (ML) determination with the threshold value of “0” is not performed, as shown in FIG. 3, the multiplexed signal _Fi is a binary multiplexed signal 23 having logical values = “− 1” and “1”. (The multiplexed signal F _{i of} logical value = “− 1”, “1”) can be limited. As a result, the majority logic decision unit 16 shown in FIG.
In (ML), the binary multiplexed signal 23 having only the logical value = “− 1” and “1” (the multiplexed signal F _{i having the} logical value = “− 1” and “1”)
Therefore, the transmission unit 18 and the reception unit 19 shown in FIG. 1 can be configured by digital devices, a simple system can be constructed, and maintenance can be improved and the size can be reduced. Such a spread spectrum communication device 10 can improve the consistency with the TDMA system used as the mainstream of the in-vehicle multiplex communication system in trains and automobiles.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings. The same parts as those already described in the first embodiment are denoted by the same reference numerals, and the duplicate description will be omitted.

In the present embodiment, a Hadamard matrix H _k , which is a kind of orthogonal code, is set to a spreading code P to reduce the inter-channel interference during majority logic spread spectrum multiplexing communication to zero.
Instead of techniques used as N _i, the Hadamard matrix H
_k modified second Hadamard matrix J excluding the first column
It is characterized in that _k (k = positive integer) is used as the spreading code PN _i .

Specifically, when the value of k is 2, the second
Modified Hadamard matrix J ₂ of the matrix as shown in Equation 6.

[0040]

(Equation 6)

As described above, by assigning the second modified Hadamard matrix J _k excluding the first column of the Hadamard matrix H _k to the spreading code PN _i , the orthogonality of each column vector 11 is lost, but the since the orthogonality of the vector 13 can be held, it becomes possible to always execute the odd multiple by avoiding the even multiple in performing multiplexed using orthogonal codes, such as Hadamard matrix H _k. As a result, it eliminates the case in which multi-value level of the multiplex signal F _i at the time of the majority logic spread spectrum multiplex communication becomes logical value = "0".

Also, after the assignment, the majority logic (M) is used as shown in FIGS.
L) When the judgment is performed, the majority logic (ML) judgment with the logical value = “0” as the threshold is not executed,
As shown in FIG. 3, the multiplex signal _Fi has a logical value = “− 1”,
Binary multiplexed signal 23 of “1” (logical value = “− 1”, “1”
Multiplexed signal F _i ). as a result,
The majority logic decision unit 16 (ML) shown in FIG.
Binary multiplexed signal 23 of only "-1" and "1" (logical value =
Since it is possible to obtain a multiplexed signal F _i ) of “−1” and “1”, the transmitting unit 18 and the receiving unit 19 shown in FIG. 1 can be configured by digital devices, and a simple system can be constructed. It is possible to improve the maintainability and reduce the size.
Such a spread spectrum communication apparatus 10 can improve the consistency with the time division multiplexing (TDMA) system used as the mainstream of the in-vehicle multiplex communication system in trains and automobiles.

It is apparent that the present invention is not limited to the above embodiments, and that the above embodiments can be appropriately modified within the scope of the technical idea of the present invention. Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to numbers, positions, shapes, and the like suitable for carrying out the present invention. In each drawing, the same components are denoted by the same reference numerals.

[0044]

Since the present invention is configured as described above, the following effects can be obtained. A first effect is that majority logic spread spectrum multiplexing communication with zero inter-channel interference can be realized.

The second effect is that it is possible to obtain a binary multiplexed signal having only logical values "-1" and "1" in the majority logic decision section, so that the transmitting section and the receiving section can be provided by a digital device. As a result, a simple system can be constructed, and maintenance performance can be improved and the size can be reduced.

The third effect is that the consistency with the time division multiplexing (TDMA) system used as the mainstream of the in-vehicle multiplex communication system in trains and automobiles can be improved.

[Brief description of the drawings]

FIG. 1 is a functional block diagram for explaining a main part of a spread spectrum communication apparatus according to one embodiment of the present invention.

FIG. 2 is a state diagram of a multiplexed signal before majority logic decision in the majority logic spread spectrum multiplexing communication method according to one embodiment of the present invention.

FIG. 3 is a state diagram of a multiplexed signal after majority logic determination in the majority logic spread spectrum multiplexing communication method according to one embodiment of the present invention.

FIG. 4 is a functional block diagram for explaining a main part of a spread spectrum communication apparatus according to a second conventional technique.

FIG. 5 is a state diagram of a multiplexed signal before majority logic decision in the spread spectrum communication apparatus of the second prior art.

FIG. 6 is a state diagram of a multiplexed signal after majority logic decision in the spread spectrum communication apparatus of the second prior art.

[Explanation of symbols]

Reference Signs List 10 spread spectrum communication apparatus 11 column vector 13 row vector F _i (i = 1,..., N: i, N is a positive integer) multiplexed signal 16 majority logic decision unit 18 transmission unit 19 reception unit 23 binary multiplexed signal 27 ternary multiplexed signal H _k (k = positive integer) Hadamard matrix I _k (k = positive integer) first modified Hadamard matrix J _k (k = positive integer) Second modified Hadamard matrix PN _i (i = 1,..., N: i, N is a positive integer) spread code SG _i (i = 1,..., N: i, N is a positive integer) information code

Claims (5)

[Claims] 1. A transmitting unit and a receiving unit for performing majority logic spread spectrum multiplex communication, and generating and outputting a first modified Hadamard matrix excluding a first row of a Hadamard matrix during the majority logic spread spectrum multiplex communication. Means for generating a spread code using the first modified Hadamard matrix.
A spread-spectrum communication device, comprising: a means for outputting a decision signal; and a majority logic decision unit for executing a majority logic decision based on the spread code and generating and outputting a binary multiplexed signal represented by two types of logic values. . 2. A transmitting unit and a receiving unit for performing majority logic spread spectrum multiplex communication, and generating and outputting a second modified Hadamard matrix excluding the first column of the Hadamard matrix during the majority logic spread spectrum multiplex communication. Means for generating a spread code using the second modified Hadamard matrix.
A spread-spectrum communication device, comprising: a means for outputting a decision signal; and a majority logic decision unit for executing a majority logic decision based on the spread code and generating and outputting a binary multiplexed signal represented by two types of logic values. . 3. The spread spectrum communication according to claim 1, wherein a logical value of the binary multiplexed signal generated and output by the majority logic decision unit is two values of −1 and 1. apparatus. 4. A step of executing majority logic spread spectrum multiplexing communication using a transmitting unit and a receiving unit; and performing a first modified Hadamard matrix excluding the first row of the Hadamard matrix during the majority logic spread spectrum multiplexing communication. Generating and outputting; a step of generating and outputting a spread code using the first modified Hadamard matrix; performing a majority logic decision based on the spread code; A majority logic spread spectrum multiplexing communication method, comprising a majority logic decision step for generating and outputting a binary multiplexed signal represented by a value. 5. A step of executing majority logic spread spectrum multiplexing communication using a transmitting unit and a receiving unit, and performing a second modified Hadamard matrix excluding the first column of the Hadamard matrix during the majority logic spread spectrum multiplexing communication. Generating and outputting; generating and outputting a spread code using the second modified Hadamard matrix; performing a majority logic decision based on the spread code; A majority logic spread spectrum multiplexing communication method, comprising a majority logic decision step for generating and outputting a binary multiplexed signal represented by a value.